Premium Fuel Recommended

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Originally Posted By: gathermewool
Originally Posted By: rg200amp
I agree with everything but these two statements:

Originally Posted By: gathermewool
Higher grade fuels do NOT have more or better detergents.


First, Higher octane fuels do have more detergents for the most part:
BP fuel offers there degergents in all there grades, but the high octane has the highest amount.
http://www.bp.com/heliospower/sectiongenericarticle.do?categoryId=9024438&contentId=7045600
"Amoco Ultimate is our highest-octane gasoline, and now it also has the highest concentration of Invigorate. It’s been proven in side-by-side tests to keep valves and fuel injectors nearly “new engine” clean with continuous use."

And Shell only offers its V-power detergents in there high octane grade:
http://www.shell.us/home/content/usa/pro...about_tabs.html
What is the octane rating of Shell V-Power?
Octane ratings for premium gasoline vary across the country. The octane level of Shell V-Power is anywhere from 90 to 93 octane, depending on the region. It’s important to point out, however, that octane is not the only factor to consider when choosing a fuel. For example, many cars that don’t require higher octane can benefit from the cleaning power provided by Shell V-Power.


Originally Posted By: gathermewool
Its higher octane number simply makes it less prone to detonation. This means that when the fuel is injected into the cylinder full of hot, compressed air it won't ignite on its own


Yes, less prone to detonation. Its not the "Cylinder full of hot, compressed air" that causes detonation. Its the actual action of compression. In a high compression engine, a low octane fuel, like diesel fuel can/will ignite from just the action of the cylinder compressing the air and fuel mix.


What happens to air (or any gas) when it's compressed??? For a fixed volume, when a gas is compressed its temperature will raise. When a volatile, low octane fuel is injected into a very hot volume of compressed air, it can potentially ignite BEFORE the spark plug causes ignition. This is detonation, and what I was talking about.

I was wrong about additive being the same for all grades. Sorry about that : )


thumbsup2.gif
 
Originally Posted By: gathermewool
Originally Posted By: rg200amp
I agree with everything but these two statements:

Originally Posted By: gathermewool
Higher grade fuels do NOT have more or better detergents.


First, Higher octane fuels do have more detergents for the most part:
BP fuel offers there degergents in all there grades, but the high octane has the highest amount.
http://www.bp.com/heliospower/sectiongenericarticle.do?categoryId=9024438&contentId=7045600
"Amoco Ultimate is our highest-octane gasoline, and now it also has the highest concentration of Invigorate. It’s been proven in side-by-side tests to keep valves and fuel injectors nearly “new engine” clean with continuous use."

And Shell only offers its V-power detergents in there high octane grade:
http://www.shell.us/home/content/usa/pro...about_tabs.html
What is the octane rating of Shell V-Power?
Octane ratings for premium gasoline vary across the country. The octane level of Shell V-Power is anywhere from 90 to 93 octane, depending on the region. It’s important to point out, however, that octane is not the only factor to consider when choosing a fuel. For example, many cars that don’t require higher octane can benefit from the cleaning power provided by Shell V-Power.


Originally Posted By: gathermewool
Its higher octane number simply makes it less prone to detonation. This means that when the fuel is injected into the cylinder full of hot, compressed air it won't ignite on its own


Yes, less prone to detonation. Its not the "Cylinder full of hot, compressed air" that causes detonation. Its the actual action of compression. In a high compression engine, a low octane fuel, like diesel fuel can/will ignite from just the action of the cylinder compressing the air and fuel mix.


What happens to air (or any gas) when it's compressed??? For a fixed volume, when a gas is compressed its temperature will raise. When a volatile, low octane fuel is injected into a very hot volume of compressed air, it can potentially ignite BEFORE the spark plug causes ignition. This is detonation, and what I was talking about.

I was wrong about additive being the same for all grades. Sorry about that : )


I see what your saying. But it sounds like your saying "fuel is injected into a very hot volume of compressed air" thus it can ignite.

What I am saying is it is not the "very hot volume of compressed air" causing the preignition.
Like you said: "For a fixed volume, when a gas is compressed its temperature will raise"
It's the action(key word) of the fuel and air being compressed that can cause preignition.
Thus high compression engines need high octane. The compression causes preignition with low octance.

I think we both are leaning towards the same concept, were just having communication issues!
cheers3.gif
 
no no no. You're not gonna get out of this that easily! We don't need no stinkin communi...what'd you call it? : P
 
Originally Posted By: gathermewool
no no no. You're not gonna get out of this that easily! We don't need no stinkin communi...what'd you call it? : P
LOL.gif
 
Not to go off topic here, but say a car recommends 87 AKI and you use a higher octane fuel. What would the consequences be? From my understanding, the higher the octane, the harder it is to burn and if your timing is not set for higher octane fuel, there's really no point to it. I reckon a drop in MPG and an increase in fuel expenditure would be the result?
54.gif
 
Premium isn't harder to burn, it's harder to pre-ignite under compression without spark. With spark it will burn the same as 87 only cleaner.
 
Originally Posted By: Neil_A
Premium isn't harder to burn, it's harder to pre-ignite under compression without spark. With spark it will burn the same as 87 only cleaner.


Yes and No.

It will work. But if a car is tuned to 87, The car can see a drop in MPG.

Run what the engine is made to run. You will get the best performance and MPG that way.

Too, high octane fuel burns slower than 87. Yes it is milliseconds we are talking here, but if your timing is set for 87, and you run 93, you may not only see a slight MPG drop, but a slight performance drop aswell. It depends on the car, engine, and CPU.
 
I still fail to understand how higher octane "burns cleaner". A lot of people say to avoid fuel system cleaners and just switch to a higher octane fuel to "keep your injectors clean". If it burns slower, costs more and causes your MPG/performance to suffer, then what advantages does it have?

Also, this is straight out of the owners manual for my Montero:

Quote:
Your vehicle is designed to operate on unleaded gasoline, with a minimum octane rating of 91 RON.


The fuel door has a label which reads "91 RON or Higher". When they use words like "minimum octane rating" and "or higher", does this mean 91 RON works fine, but they recommend a higher octane fuel? The way they put it is rather confusing.

My father always used 95 RON, until I told him 91 is the grade that should be used. Am I wrong?
54.gif
The engine does seem to run smoother with 91 RON, however.
 
Originally Posted By: rg200amp
Originally Posted By: Neil_A
Premium isn't harder to burn, it's harder to pre-ignite under compression without spark. With spark it will burn the same as 87 only cleaner.


Yes and No.

It will work. But if a car is tuned to 87, The car can see a drop in MPG.

Run what the engine is made to run. You will get the best performance and MPG that way.

Too, high octane fuel burns slower than 87. Yes it is milliseconds we are talking here, but if your timing is set for 87, and you run 93, you may not only see a slight MPG drop, but a slight performance drop aswell. It depends on the car, engine, and CPU.


Premium doesn't burn slower, it's just more resistant to compression ignition. The old 114 octane I ran years ago had a quicker burn rate than regular gas.

The only downside to running higher than recommended octane is the cost.
 
Originally Posted By: Falcon_LS
I still fail to understand how higher octane "burns cleaner". A lot of people say to avoid fuel system cleaners and just switch to a higher octane fuel to "keep your injectors clean". If it burns slower, costs more and causes your MPG/performance to suffer, then what advantages does it have?

Also, this is straight out of the owners manual for my Montero:

Quote:
Your vehicle is designed to operate on unleaded gasoline, with a minimum octane rating of 91 RON.


The fuel door has a label which reads "91 RON or Higher". When they use words like "minimum octane rating" and "or higher", does this mean 91 RON works fine, but they recommend a higher octane fuel? The way they put it is rather confusing.

My father always used 95 RON, until I told him 91 is the grade that should be used. Am I wrong?
54.gif
The engine does seem to run smoother with 91 RON, however.



People say it is "cleaner" for the engine because most gas stations offer more detergents in there high octane fuel. This is not allways the case, and its not a reason people should use it if there car does not spec it.


Your other question:
The car maker has to put a minimum octane rating. If you want to use 2-3 points higher, it will not harm anything. I use 93 octane. My car specs 91 or higher.
 
Originally Posted By: BuickGN

Premium doesn't burn slower


I am not the only one who thinks so. . .


http://www.state.mn.us/portal/mn/jsp/con...agency=Commerce
"High octane gasoline burns slower than low octane gasoline. The slow burn prevents engine knock when cylinder pressures are high."

http://www.handymanusa.com/articles/octane.html
"High octane gasoline burns slower than low octane gasoline"

http://www.tricktuners.com/detonation_explained.htm
"High octane fuel burns slower than low octane, and high octane is much more resistant to higher pressures and temperatures."

http://www.ourautoshop.com/GasFacts.html
"High-octane fuels burn slower"
 
Originally Posted By: rg200amp
Originally Posted By: BuickGN

Premium doesn't burn slower


I am not the only one who thinks so. . .


http://www.state.mn.us/portal/mn/jsp/con...agency=Commerce
"High octane gasoline burns slower than low octane gasoline. The slow burn prevents engine knock when cylinder pressures are high."

http://www.handymanusa.com/articles/octane.html
"High octane gasoline burns slower than low octane gasoline"

http://www.tricktuners.com/detonation_explained.htm
"High octane fuel burns slower than low octane, and high octane is much more resistant to higher pressures and temperatures."

http://www.ourautoshop.com/GasFacts.html
"High-octane fuels burn slower"


I hate to say it, but they're flat out wrong. Yes, some fuels burn faster than others, some of the slower ones might be higher octanes but the slower burn does not make a gas have a higher octane.

I've had long conversations with people from VP which supplied me with burn rates of their fuels and regular pump gas. Like I mentioned, their 114 octane burns faster than regular gas and is obviously higher in octane.
 
Originally Posted By: BuickGN
Originally Posted By: rg200amp
Originally Posted By: BuickGN

Premium doesn't burn slower


I am not the only one who thinks so. . .


http://www.state.mn.us/portal/mn/jsp/con...agency=Commerce
"High octane gasoline burns slower than low octane gasoline. The slow burn prevents engine knock when cylinder pressures are high."

http://www.handymanusa.com/articles/octane.html
"High octane gasoline burns slower than low octane gasoline"

http://www.tricktuners.com/detonation_explained.htm
"High octane fuel burns slower than low octane, and high octane is much more resistant to higher pressures and temperatures."

http://www.ourautoshop.com/GasFacts.html
"High-octane fuels burn slower"


I hate to say it, but they're flat out wrong. Yes, some fuels burn faster than others, some of the slower ones might be higher octanes but the slower burn does not make a gas have a higher octane.

I've had long conversations with people from VP which supplied me with burn rates of their fuels and regular pump gas. Like I mentioned, their 114 octane burns faster than regular gas and is obviously higher in octane.


If you google/yahoo search it, every artical on the net confirms high octane burns slower.
Theres no evidence to say other wise that I am aware of. . .

Too each his own.
 
Originally Posted By: rg200amp
Originally Posted By: BuickGN
Originally Posted By: rg200amp
Originally Posted By: BuickGN

Premium doesn't burn slower


I am not the only one who thinks so. . .


http://www.state.mn.us/portal/mn/jsp/con...agency=Commerce
"High octane gasoline burns slower than low octane gasoline. The slow burn prevents engine knock when cylinder pressures are high."

http://www.handymanusa.com/articles/octane.html
"High octane gasoline burns slower than low octane gasoline"

http://www.tricktuners.com/detonation_explained.htm
"High octane fuel burns slower than low octane, and high octane is much more resistant to higher pressures and temperatures."

http://www.ourautoshop.com/GasFacts.html
"High-octane fuels burn slower"


I hate to say it, but they're flat out wrong. Yes, some fuels burn faster than others, some of the slower ones might be higher octanes but the slower burn does not make a gas have a higher octane.

I've had long conversations with people from VP which supplied me with burn rates of their fuels and regular pump gas. Like I mentioned, their 114 octane burns faster than regular gas and is obviously higher in octane.


If you google/yahoo search it, every artical on the net confirms high octane burns slower.
Theres no evidence to say other wise that I am aware of. . .

Too each his own.




That's the internet for you. Take it with a grain of salt.

I can see why you would think that because there are so many sites out there saying this. If it weren't for talking to the tech guys at VP during a tech session at one of our club meets I would've thought the same. It's as bad of a myth as the old K&N filter= better mileage on a fuel injected car.

This is not to say that *some* higher octanes don't have a slower burn rate than some lower octanes.
 
I have a 01 ES300 with the same engine with OP's RX300 -> 1MZ-FE and can tell the diff. b/w regular v.s. prem.

If I switch instantly from a tank of 87 to 91, I won't feel much of a diff unless I reset your ECU (by pulling EFI fuse.) ECU must re-learn this new gas. However, if I switch instantly from 91 to 87, I will feel power loss.

Gas mileage up about ~5-7% if I up premium instead of regular and reset ECU. This was over 5 tanks of premium fuel. I also notice that prem give more benefit in hotter days that colder days so I use regular in winter (CA here) and use premium in summer.
 
Originally Posted By: rg200amp

If you google/yahoo search it, every artical on the net confirms high octane burns slower.
Theres no evidence to say other wise that I am aware of. . .

Too each his own.


I think the problem is just the term "burns slower" that is loosely used.
If this burn slower is refered to high flash point, I think the Internet source is right, but it may not be accurate if it is taken "literally".

High octane fuel flash point is higher than regular but normally will burn faster depends on the molecules contents.
 
Last edited:
Originally Posted By: delta901
I have a 01 ES300 with the same engine with OP's RX300 -> 1MZ-FE and can tell the diff. b/w regular v.s. prem.

If I switch instantly from a tank of 87 to 91, I won't feel much of a diff unless I reset your ECU (by pulling EFI fuse.) ECU must re-learn this new gas. However, if I switch instantly from 91 to 87, I will feel power loss.

Gas mileage up about ~5-7% if I up premium instead of regular and reset ECU. This was over 5 tanks of premium fuel. I also notice that prem give more benefit in hotter days that colder days so I use regular in winter (CA here) and use premium in summer.


I think you are right, with colder climate the engine can take lower octane better. Japan also sell 100 RON fuel on the normal gas station, that is why many Japan ECU have pre-programmed MAP for higher octane to optimize the output.
 
Originally Posted By: delta901
I have a 01 ES300 with the same engine with OP's RX300 -> 1MZ-FE and can tell the diff. b/w regular v.s. prem.

If I switch instantly from a tank of 87 to 91, I won't feel much of a diff unless I reset your ECU (by pulling EFI fuse.) ECU must re-learn this new gas. However, if I switch instantly from 91 to 87, I will feel power loss.

Gas mileage up about ~5-7% if I up premium instead of regular and reset ECU. This was over 5 tanks of premium fuel. I also notice that prem give more benefit in hotter days that colder days so I use regular in winter (CA here) and use premium in summer.


delta,
Does the ECU need to be reset or will it just take longer for it to learn and adjust for the difference in the higher octane?
 
They're all different but they will eventually go back to full timing. This process shouldn't take more than a few minutes for most cars but I've heard some can take a day or so of driving.
 
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