Up until 4 or 5 years ago, we used to be able to buy 85 Octane gas here in NY state at the Oneida nation gas stations.
I'm done with low octane fuel
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Originally Posted by Miller88
Up until 4 or 5 years ago, we used to be able to buy 85 Octane gas here in NY state at the Oneida nation gas stations.
Not sure if that might be something that could be done with some cars with lower octane demands. I remember the '89 Integra I drove in college had an 86 octane requirement, but I remember it said that lower was acceptable at higher altitude. My wife's 2002 Civic owners manual says the same thing. I wonder if that would have a knock sensor that would protect it.
Up until 4 or 5 years ago, we used to be able to buy 85 Octane gas here in NY state at the Oneida nation gas stations.
Not sure if that might be something that could be done with some cars with lower octane demands. I remember the '89 Integra I drove in college had an 86 octane requirement, but I remember it said that lower was acceptable at higher altitude. My wife's 2002 Civic owners manual says the same thing. I wonder if that would have a knock sensor that would protect it.
Originally Posted by ofelas
I believe MaintenanceMan was (correctly) referring to ethanol being used to boost a lower octane gasoline up to an 87 rating at the pump.
A farm subsidy at it's best.
I stand by my post #5015095. 114 octane ethanol is NOT needed in an 87 octane designed gasoline engine. 87 octane ethanol-free gasoline is what is needed in an 87 octane designed gasoline engine. 87 octane ethanol blend fuel(E10) is by definition a blend of 114 octane ethanol component & 84 octane gasoline component. Neither component is 87 octane, & both components provide sub-standard MPG & performance in 87 octane gasoline engines that engineers designed to best burn 87 octane ethanol-free gasoline(E0). 114 octane ethanol can NOT "improve" or "boost" performance of 87 octane E0, which is what 87 octane gasoline engines are designed to burn most efficiently.
I believe MaintenanceMan was (correctly) referring to ethanol being used to boost a lower octane gasoline up to an 87 rating at the pump.
A farm subsidy at it's best.
I stand by my post #5015095. 114 octane ethanol is NOT needed in an 87 octane designed gasoline engine. 87 octane ethanol-free gasoline is what is needed in an 87 octane designed gasoline engine. 87 octane ethanol blend fuel(E10) is by definition a blend of 114 octane ethanol component & 84 octane gasoline component. Neither component is 87 octane, & both components provide sub-standard MPG & performance in 87 octane gasoline engines that engineers designed to best burn 87 octane ethanol-free gasoline(E0). 114 octane ethanol can NOT "improve" or "boost" performance of 87 octane E0, which is what 87 octane gasoline engines are designed to burn most efficiently.
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Originally Posted by WishIhadatruck
.....I've tried 93 octane in every car....... I never noticed a difference in power or fuel economy with the exception of my 2014 Cruze Eco MT....I typically run 89 octane when it warms up in the spring, once it gets over 70 deg. F, I run 93 octane. I get better fuel economy and the engine runs much smoother.
Oh, at one time I really wanted an Eco Cruze MT. I wanted the 50MPG, some people got. Since you didn't mention ethanol-free gasoline, I assume you used 87 octane, 89 octane & 93 octane ethanol blends(E10), at different times. More accurately, 87 octane E10 is a blend of 114 octane ethanol & 84 octane gasoline. 89 octane E10 is a blend of 114 octane ethanol & 86+ octane gasoline. 93 octane E10 is a blend of 114 octane ethanol & 90+ octane gasoline. Best performance & MPG would have been burning 87 octane ethanol-free gasoline (E0), 89 octane ethanol-free gasoline(E0), or 93 octane ethanol-free gasoline(E0). On average, I believe that E0 would give better MPG than E10, for feather-footers, not as much of a difference for lead-footers. Michigan has quite a bit of E0. Give it a try. (Oh, wow! Michigan has 450 E0 sources. Not many years ago, they had less than 200 E0 sources. Good luck, hunting for E0.)
.....I've tried 93 octane in every car....... I never noticed a difference in power or fuel economy with the exception of my 2014 Cruze Eco MT....I typically run 89 octane when it warms up in the spring, once it gets over 70 deg. F, I run 93 octane. I get better fuel economy and the engine runs much smoother.
Oh, at one time I really wanted an Eco Cruze MT. I wanted the 50MPG, some people got. Since you didn't mention ethanol-free gasoline, I assume you used 87 octane, 89 octane & 93 octane ethanol blends(E10), at different times. More accurately, 87 octane E10 is a blend of 114 octane ethanol & 84 octane gasoline. 89 octane E10 is a blend of 114 octane ethanol & 86+ octane gasoline. 93 octane E10 is a blend of 114 octane ethanol & 90+ octane gasoline. Best performance & MPG would have been burning 87 octane ethanol-free gasoline (E0), 89 octane ethanol-free gasoline(E0), or 93 octane ethanol-free gasoline(E0). On average, I believe that E0 would give better MPG than E10, for feather-footers, not as much of a difference for lead-footers. Michigan has quite a bit of E0. Give it a try. (Oh, wow! Michigan has 450 E0 sources. Not many years ago, they had less than 200 E0 sources. Good luck, hunting for E0.)
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Originally Posted by litesong
Originally Posted by ofelas
I believe MaintenanceMan was (correctly) referring to ethanol being used to boost a lower octane gasoline up to an 87 rating at the pump.
A farm subsidy at it's best.
I stand by my post #5015095. 114 octane ethanol is NOT needed in an 87 octane designed gasoline engine. 87 octane ethanol-free gasoline is what is needed in an 87 octane designed gasoline engine. 87 octane ethanol blend fuel(E10) is by definition a blend of 114 octane ethanol component & 84 octane gasoline component. Neither component is 87 octane, & both components provide sub-standard MPG & performance in 87 octane gasoline engines that engineers designed to best burn 87 octane ethanol-free gasoline(E0). 114 octane ethanol can NOT "improve" or "boost" performance of 87 octane E0, which is what 87 octane gasoline engines are designed to burn most efficiently.
Exactly correct to me.
Originally Posted by ofelas
I believe MaintenanceMan was (correctly) referring to ethanol being used to boost a lower octane gasoline up to an 87 rating at the pump.
A farm subsidy at it's best.
I stand by my post #5015095. 114 octane ethanol is NOT needed in an 87 octane designed gasoline engine. 87 octane ethanol-free gasoline is what is needed in an 87 octane designed gasoline engine. 87 octane ethanol blend fuel(E10) is by definition a blend of 114 octane ethanol component & 84 octane gasoline component. Neither component is 87 octane, & both components provide sub-standard MPG & performance in 87 octane gasoline engines that engineers designed to best burn 87 octane ethanol-free gasoline(E0). 114 octane ethanol can NOT "improve" or "boost" performance of 87 octane E0, which is what 87 octane gasoline engines are designed to burn most efficiently.
Exactly correct to me.
There was a time when the traditional way to blend fuel was to take something like an 87 octane E0, add whatever ethanol or MTBE to it, and sell it as 87. The industry called it "octane giveaway" since the oxygenate typically boosted the octane level around 2 points.
But these days it gets complicated with high demand for premium and not enough based on allocating output without wasting some. I heard that low octane fuel was one pumped back into old wells, but I don't think that's allowed any more. But key in all this is that some octane booster is critical to making this all work.
Ethanol makes sense. It's the cheapest octane booster on the market and costs less than gasoline. It's built into the commodity system with commodity fuels like RBOB specifically sold for blend with the maximum 10% ethanol to meet 87 (R+M)/2.
But these days it gets complicated with high demand for premium and not enough based on allocating output without wasting some. I heard that low octane fuel was one pumped back into old wells, but I don't think that's allowed any more. But key in all this is that some octane booster is critical to making this all work.
Ethanol makes sense. It's the cheapest octane booster on the market and costs less than gasoline. It's built into the commodity system with commodity fuels like RBOB specifically sold for blend with the maximum 10% ethanol to meet 87 (R+M)/2.
Originally Posted by Miller88
Up until 4 or 5 years ago, we used to be able to buy 85 Octane gas here in NY state at the Oneida nation gas stations.
Oh, how interesting! Examining pure-gas.org for all the addresses & details to ethanol-free gasoline(E0) around the U.S., 85 octane E0 is strongly restricted to high elevations (above 3000 feet?) in high altitude states likc S.Dakota, Wyoming, Colorado, Montana, Idaho, etc. I'm gonna get over to Idaho sometime & get some of that there 85 octane E0. Think it will be great.
Now 85 octane ethanol blend E10 is a different story. 85 octane E10 is an ethanol blend of 114 octane ethanol AND 81.8 octane gasoline. Don't want any 81.8 octane gasoline in my engine, even at altitude.
Up until 4 or 5 years ago, we used to be able to buy 85 Octane gas here in NY state at the Oneida nation gas stations.
Oh, how interesting! Examining pure-gas.org for all the addresses & details to ethanol-free gasoline(E0) around the U.S., 85 octane E0 is strongly restricted to high elevations (above 3000 feet?) in high altitude states likc S.Dakota, Wyoming, Colorado, Montana, Idaho, etc. I'm gonna get over to Idaho sometime & get some of that there 85 octane E0. Think it will be great.
Now 85 octane ethanol blend E10 is a different story. 85 octane E10 is an ethanol blend of 114 octane ethanol AND 81.8 octane gasoline. Don't want any 81.8 octane gasoline in my engine, even at altitude.
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Originally Posted by litesong
Originally Posted by ofelas
I believe MaintenanceMan was (correctly) referring to ethanol being used to boost a lower octane gasoline up to an 87 rating at the pump.
A farm subsidy at it's best.
I stand by my post #5015095. 114 octane ethanol is NOT needed in an 87 octane designed gasoline engine. 87 octane ethanol-free gasoline is what is needed in an 87 octane designed gasoline engine. 87 octane ethanol blend fuel(E10) is by definition a blend of 114 octane ethanol component & 84 octane gasoline component. Neither component is 87 octane, & both components provide sub-standard MPG & performance in 87 octane gasoline engines that engineers designed to best burn 87 octane ethanol-free gasoline(E0). 114 octane ethanol can NOT "improve" or "boost" performance of 87 octane E0, which is what 87 octane gasoline engines are designed to burn most efficiently.
Thing is, the only vendor of E0 in my area is Walmart's Murphy USA, and they want more for it than 93 octane, so it's pretty expensive. Last time I checked E0 was close to $3 a gallon and E10 87 was under $2. I'm sure I would get a little higher economy with it owing to the higher BTU content of ethanol free gas, however, the cost does not justify the additional efficiency gained. And since my car runs fine on regular E10 87, I'm going to keep running it.
Where I do use E0 is in my outdoor power equipment. The E0 gas doesn't go bad in the carbs like the E10 does when you leave it sitting there over long periods, thereby eliminating many starting and running problems common with small engines using E10. A 2.5 gallon can of E0 will last me all season, so the incremental cost is minor in exchange for the benefits.
Originally Posted by ofelas
I believe MaintenanceMan was (correctly) referring to ethanol being used to boost a lower octane gasoline up to an 87 rating at the pump.
A farm subsidy at it's best.
I stand by my post #5015095. 114 octane ethanol is NOT needed in an 87 octane designed gasoline engine. 87 octane ethanol-free gasoline is what is needed in an 87 octane designed gasoline engine. 87 octane ethanol blend fuel(E10) is by definition a blend of 114 octane ethanol component & 84 octane gasoline component. Neither component is 87 octane, & both components provide sub-standard MPG & performance in 87 octane gasoline engines that engineers designed to best burn 87 octane ethanol-free gasoline(E0). 114 octane ethanol can NOT "improve" or "boost" performance of 87 octane E0, which is what 87 octane gasoline engines are designed to burn most efficiently.
Thing is, the only vendor of E0 in my area is Walmart's Murphy USA, and they want more for it than 93 octane, so it's pretty expensive. Last time I checked E0 was close to $3 a gallon and E10 87 was under $2. I'm sure I would get a little higher economy with it owing to the higher BTU content of ethanol free gas, however, the cost does not justify the additional efficiency gained. And since my car runs fine on regular E10 87, I'm going to keep running it.
Where I do use E0 is in my outdoor power equipment. The E0 gas doesn't go bad in the carbs like the E10 does when you leave it sitting there over long periods, thereby eliminating many starting and running problems common with small engines using E10. A 2.5 gallon can of E0 will last me all season, so the incremental cost is minor in exchange for the benefits.
Originally Posted by y_p_w
Ethanol makes sense. It's the cheapest octane booster on the market and costs less than gasoline. It's built into the commodity system with commodity fuels like RBOB specifically sold for blend with the maximum 10% ethanol to meet 87 (R+M)/2.
No, it does not. The federal government gives huge subsidies for ethanol production. Just because I use E10 87 doesn't mean I like the fact that it's heavily subsidized. In effect you're paying for 10% of your gas twice, once through your income taxes and once at the pump. And then again gas is taxed at the pump, so then you pay again.
Remove the subsidy and see where we stand. Maybe Ethanol continues to be used, maybe not.
Ethanol makes sense. It's the cheapest octane booster on the market and costs less than gasoline. It's built into the commodity system with commodity fuels like RBOB specifically sold for blend with the maximum 10% ethanol to meet 87 (R+M)/2.
No, it does not. The federal government gives huge subsidies for ethanol production. Just because I use E10 87 doesn't mean I like the fact that it's heavily subsidized. In effect you're paying for 10% of your gas twice, once through your income taxes and once at the pump. And then again gas is taxed at the pump, so then you pay again.
Remove the subsidy and see where we stand. Maybe Ethanol continues to be used, maybe not.
Originally Posted by SR5
I often run higher octane fuel, 95 RON / 85 MON / 90 AKI as according to the owners manual I get a 2.2% increase in power and a 3% increase in torque, it's not much but you can feel it and the tank seems to last longer.
My car has what they call "selective knock control".
Here the regular stuff is 91 RON / 82 MON / 87 AKI
Nearly all cars have that these days - even cars designed to run on regular.
Sometimes it's also a matter of marketing. My parents drive a 2001 Camry V6. The owners manual says that 87 AKI is required but more (up to 91) will increase performance and fuel economy. But my WRX says 91 recommended, but that 87 can be used without damage. They're describing about the same technical situation but explaining it in different ways.
I often run higher octane fuel, 95 RON / 85 MON / 90 AKI as according to the owners manual I get a 2.2% increase in power and a 3% increase in torque, it's not much but you can feel it and the tank seems to last longer.
My car has what they call "selective knock control".
Here the regular stuff is 91 RON / 82 MON / 87 AKI
Nearly all cars have that these days - even cars designed to run on regular.
Sometimes it's also a matter of marketing. My parents drive a 2001 Camry V6. The owners manual says that 87 AKI is required but more (up to 91) will increase performance and fuel economy. But my WRX says 91 recommended, but that 87 can be used without damage. They're describing about the same technical situation but explaining it in different ways.
Originally Posted by litesong
Originally Posted by Miller88
Up until 4 or 5 years ago, we used to be able to buy 85 Octane gas here in NY state at the Oneida nation gas stations.
Oh, how interesting! Examining pure-gas.org for all the addresses & details to ethanol-free gasoline(E0) around the U.S., 85 octane E0 is strongly restricted to high elevations (above 3000 feet?) in high altitude states likc S.Dakota, Wyoming, Colorado, Montana, Idaho, etc. I'm gonna get over to Idaho sometime & get some of that there 85 octane E0. Think it will be great.
Now 85 octane ethanol blend E10 is a different story. 85 octane E10 is an ethanol blend of 114 octane ethanol AND 81.8 octane gasoline. Don't want any 81.8 octane gasoline in my engine, even at altitude.
We're only at about 400 foot elevation. I think they were just allowed to sell cheaper gas.
Right now I live on a lake. All of the gas stations around sell ethanol free 90 octane. It's nice to be able to use in OPE
Originally Posted by Miller88
Up until 4 or 5 years ago, we used to be able to buy 85 Octane gas here in NY state at the Oneida nation gas stations.
Oh, how interesting! Examining pure-gas.org for all the addresses & details to ethanol-free gasoline(E0) around the U.S., 85 octane E0 is strongly restricted to high elevations (above 3000 feet?) in high altitude states likc S.Dakota, Wyoming, Colorado, Montana, Idaho, etc. I'm gonna get over to Idaho sometime & get some of that there 85 octane E0. Think it will be great.
Now 85 octane ethanol blend E10 is a different story. 85 octane E10 is an ethanol blend of 114 octane ethanol AND 81.8 octane gasoline. Don't want any 81.8 octane gasoline in my engine, even at altitude.
We're only at about 400 foot elevation. I think they were just allowed to sell cheaper gas.
Right now I live on a lake. All of the gas stations around sell ethanol free 90 octane. It's nice to be able to use in OPE
I suppose small engines were mentioned. I don't know if I'd ever think of spending that kind of money on regular use, but I was thinking it in the absence of non-oxygenated fuel that it might make sense to simply run some specialty small engine fuel at the end of the season before placing in storage.
Since I am giving away the power I paid for by getting the performance version of this econobox, (if i use less than 91/93 octane fuel), I will use it exclusively in this ride.
The car already gets good fuel mileage for it's given performance, even when driven aggressively (as compared to the lower cost per gallon 87 octane which they run, but much lower fuel economy roads tanks everyone else insists on driving here), so I do not mind the extra ~ 30 cents per gallon.
The car already gets good fuel mileage for it's given performance, even when driven aggressively (as compared to the lower cost per gallon 87 octane which they run, but much lower fuel economy roads tanks everyone else insists on driving here), so I do not mind the extra ~ 30 cents per gallon.
Originally Posted by billt460
Same here. All I use 91 Octane in all 3 of my vehicles, and have for years. Just like all of you, I've noticed the much better performance and mileage.
^^^^^
I agree. My Grey Goose is recommended to have 91 or higher octane level. And that's all it has gotten. One interesting note is with my scan tool I can tell the difference between gasoline in terms of misfire counts per cylinder... And Exxon gas has the lowest count of all the gas I have run. Shell 93, BP Amoco 93 and a gasoline from a grocery store... Exxon is the best in terms of having hardly any misfires in any of the 6 cylinders. Shell would have 5-13 in 140 miles of driving. Exxon is 0-3. That I find has a bit interesting. And it has been consistent over the past several months of looking at the feedback from the scan tool.
Same here. All I use 91 Octane in all 3 of my vehicles, and have for years. Just like all of you, I've noticed the much better performance and mileage.
^^^^^
I agree. My Grey Goose is recommended to have 91 or higher octane level. And that's all it has gotten. One interesting note is with my scan tool I can tell the difference between gasoline in terms of misfire counts per cylinder... And Exxon gas has the lowest count of all the gas I have run. Shell 93, BP Amoco 93 and a gasoline from a grocery store... Exxon is the best in terms of having hardly any misfires in any of the 6 cylinders. Shell would have 5-13 in 140 miles of driving. Exxon is 0-3. That I find has a bit interesting. And it has been consistent over the past several months of looking at the feedback from the scan tool.
Originally Posted by Brons2
litesong said:
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Originally Posted by litesong
The successful "ethanol in gasoline industry" propaganda campaign, that 87 octane E10 can be labeled as 87 octane is a lie.
I used to run octane rating tests in college, are you saying the E10 sold with an R+M rating of 87 isn't actually 87?
Looking through your other posts in this thread leads me to believe you don't know what an octane rating/number actually means, nor do you know how it is determined.
The successful "ethanol in gasoline industry" propaganda campaign, that 87 octane E10 can be labeled as 87 octane is a lie.
I used to run octane rating tests in college, are you saying the E10 sold with an R+M rating of 87 isn't actually 87?
Looking through your other posts in this thread leads me to believe you don't know what an octane rating/number actually means, nor do you know how it is determined.
Originally Posted by dbias
That's what I think also as the higher the octane the harder it is to ignite so it may not ignite off of a small piece of carbon jumping off of the piston. I do notice a slight increase in mpg so it's not all bad.
We need to stop these rumors. High octane gas is not harder to ignite or slower to burn, it is ONLY affecting the fuel's tendency to auto-ignite under high compression. High octane fuel resists compression ignition better than low octane. This allows high compression engines to take advantage of the available higher efficiency, and produce more power for the same engine displacement. A spark plug will ignite high octane as easily as lower octane gas. But high octane fuel can resist high compression without auto-ignition.
Most modern engines have knock sensors that allow a certain amount of ignition advance using higher octane fuel, but the compression ratio will not change. This is why you won't get your money's worth out of high octane in a regular engine, even if it does produce slightly more power and better MPGs. The engine is not designed for the high octane fuel (i.e. it is not a high compression engine), so it may run slightly better but it cannot take full advantage of the octane.
I hope this makes sense.
That's what I think also as the higher the octane the harder it is to ignite so it may not ignite off of a small piece of carbon jumping off of the piston. I do notice a slight increase in mpg so it's not all bad.
We need to stop these rumors. High octane gas is not harder to ignite or slower to burn, it is ONLY affecting the fuel's tendency to auto-ignite under high compression. High octane fuel resists compression ignition better than low octane. This allows high compression engines to take advantage of the available higher efficiency, and produce more power for the same engine displacement. A spark plug will ignite high octane as easily as lower octane gas. But high octane fuel can resist high compression without auto-ignition.
Most modern engines have knock sensors that allow a certain amount of ignition advance using higher octane fuel, but the compression ratio will not change. This is why you won't get your money's worth out of high octane in a regular engine, even if it does produce slightly more power and better MPGs. The engine is not designed for the high octane fuel (i.e. it is not a high compression engine), so it may run slightly better but it cannot take full advantage of the octane.
I hope this makes sense.
Originally Posted by DGXR
Originally Posted by dbias
That's what I think also as the higher the octane the harder it is to ignite so it may not ignite off of a small piece of carbon jumping off of the piston. I do notice a slight increase in mpg so it's not all bad.
We need to stop these rumors. High octane gas is not harder to ignite or slower to burn, it is ONLY affecting the fuel's tendency to auto-ignite under high compression. High octane fuel resists compression ignition better than low octane. This allows high compression engines to take advantage of the available higher efficiency, and produce more power for the same engine displacement. A spark plug will ignite high octane as easily as lower octane gas. But high octane fuel can resist high compression without auto-ignition.
Most modern engines have knock sensors that allow a certain amount of ignition advance using higher octane fuel, but the compression ratio will not change. This is why you won't get your money's worth out of high octane in a regular engine, even if it does produce slightly more power and better MPGs. The engine is not designed for the high octane fuel (i.e. it is not a high compression engine), so it may run slightly better but it cannot take full advantage of the octane.
I hope this makes sense.
Detonation is pretty bad from what I understand. Maybe a little bit is normal and doesn't damage anything, but if it goes boom and you've got one part of the mixture exploding it can be pretty nasty what it will do to an engine.
Originally Posted by dbias
That's what I think also as the higher the octane the harder it is to ignite so it may not ignite off of a small piece of carbon jumping off of the piston. I do notice a slight increase in mpg so it's not all bad.
We need to stop these rumors. High octane gas is not harder to ignite or slower to burn, it is ONLY affecting the fuel's tendency to auto-ignite under high compression. High octane fuel resists compression ignition better than low octane. This allows high compression engines to take advantage of the available higher efficiency, and produce more power for the same engine displacement. A spark plug will ignite high octane as easily as lower octane gas. But high octane fuel can resist high compression without auto-ignition.
Most modern engines have knock sensors that allow a certain amount of ignition advance using higher octane fuel, but the compression ratio will not change. This is why you won't get your money's worth out of high octane in a regular engine, even if it does produce slightly more power and better MPGs. The engine is not designed for the high octane fuel (i.e. it is not a high compression engine), so it may run slightly better but it cannot take full advantage of the octane.
I hope this makes sense.
Detonation is pretty bad from what I understand. Maybe a little bit is normal and doesn't damage anything, but if it goes boom and you've got one part of the mixture exploding it can be pretty nasty what it will do to an engine.
Originally Posted by DGXR
Originally Posted by dbias
That's what I think also as the higher the octane the harder it is to ignite so it may not ignite off of a small piece of carbon jumping off of the piston. I do notice a slight increase in mpg so it's not all bad.
We need to stop these rumors. High octane gas is not harder to ignite or slower to burn, it is ONLY affecting the fuel's tendency to auto-ignite under high compression. High octane fuel resists compression ignition better than low octane. This allows high compression engines to take advantage of the available higher efficiency, and produce more power for the same engine displacement. A spark plug will ignite high octane as easily as lower octane gas. But high octane fuel can resist high compression without auto-ignition.
Most modern engines have knock sensors that allow a certain amount of ignition advance using higher octane fuel, but the compression ratio will not change. This is why you won't get your money's worth out of high octane in a regular engine, even if it does produce slightly more power and better MPGs. The engine is not designed for the high octane fuel (i.e. it is not a high compression engine), so it may run slightly better but it cannot take full advantage of the octane.
I hope this makes sense.
Not just high compression ratios, but also forced induction.
My 2004 WRX has a compression ratio of 8.0:1, but the pressures are higher because of the turbo. Still - I look at the newer engines and there might be a 10.6:1 ratio, plus a turbo. Back in the days of my first car a 10.0:1 ratio was considered high and usually needed premium.
Originally Posted by dbias
That's what I think also as the higher the octane the harder it is to ignite so it may not ignite off of a small piece of carbon jumping off of the piston. I do notice a slight increase in mpg so it's not all bad.
We need to stop these rumors. High octane gas is not harder to ignite or slower to burn, it is ONLY affecting the fuel's tendency to auto-ignite under high compression. High octane fuel resists compression ignition better than low octane. This allows high compression engines to take advantage of the available higher efficiency, and produce more power for the same engine displacement. A spark plug will ignite high octane as easily as lower octane gas. But high octane fuel can resist high compression without auto-ignition.
Most modern engines have knock sensors that allow a certain amount of ignition advance using higher octane fuel, but the compression ratio will not change. This is why you won't get your money's worth out of high octane in a regular engine, even if it does produce slightly more power and better MPGs. The engine is not designed for the high octane fuel (i.e. it is not a high compression engine), so it may run slightly better but it cannot take full advantage of the octane.
I hope this makes sense.
Not just high compression ratios, but also forced induction.
My 2004 WRX has a compression ratio of 8.0:1, but the pressures are higher because of the turbo. Still - I look at the newer engines and there might be a 10.6:1 ratio, plus a turbo. Back in the days of my first car a 10.0:1 ratio was considered high and usually needed premium.
Good point!
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