I just stopped by my local Sunoco and started pumping 87 octane into my truck and noticed the "smell" of gasoline, I guess it was fresh or something. Anyhoo, came back with my GLI and filled up with 93 octane and noticed a "different smell" ? There is a huge discussion about how 87 or 93 octane gasoline and if your vehicle requires premium, that you shouldn't worry about it and run 87. If they are the same, then why do they smell different?
gasoline octane doesn't matter!!!! whatever
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This is a copy of a post I made on another site:
The difference in smell is probably a different additives package. I have been told that Shell gasoline uses a radically different additives package in its premium than it does in its regular. I do not however know if thes is true. Additives in gasoline also vary county to county and state to state depending on local emission laws.
Sandlot:
Generally good info, but I'd add the following two points. First, and this is totally lost on the Consumer Reports crowd, many engines today are designed to run within acceptable parameters on either regular or premium fuel. They do so, of course, by using the knock sensors and ECU programming to adjust spark timing to the fuel used -- higher octane, more advance on the timing, lower gets more retarded timing. Both my present car (a G35) and the one before it (a V-6 Camry) fall into this category. The CR types will cry out, "see, premium isn't needed -- it's a waste". The manual, however, has language to the effect that, "87 octane fuel is acceptable, but 91 octane or higher is recommended for improved performance". In my case, I can very well feel the difference between my engines running on premium vs. regular. Premium, thanks. . .
Second, the benefit of premium continues after the spark hits. The combustion of the fuel-air mix must remain a smooth burn and not turn into a explosion. That's what generates the commonly heard "ping". What you described -- lightoff before the spark plug fires -- is actually a different and much more dangerous problem called "preignition". This is a problem which can kill an engine in very short order if it's happening with any regularity.
Generally good info, but I'd add the following two points. First, and this is totally lost on the Consumer Reports crowd, many engines today are designed to run within acceptable parameters on either regular or premium fuel. They do so, of course, by using the knock sensors and ECU programming to adjust spark timing to the fuel used -- higher octane, more advance on the timing, lower gets more retarded timing. Both my present car (a G35) and the one before it (a V-6 Camry) fall into this category. The CR types will cry out, "see, premium isn't needed -- it's a waste". The manual, however, has language to the effect that, "87 octane fuel is acceptable, but 91 octane or higher is recommended for improved performance". In my case, I can very well feel the difference between my engines running on premium vs. regular. Premium, thanks. . .
Second, the benefit of premium continues after the spark hits. The combustion of the fuel-air mix must remain a smooth burn and not turn into a explosion. That's what generates the commonly heard "ping". What you described -- lightoff before the spark plug fires -- is actually a different and much more dangerous problem called "preignition". This is a problem which can kill an engine in very short order if it's happening with any regularity.
The post was made on a site full of younger guys who not only argued with the points I made but flat out refused to accept them. I tried to dumb it down enough for them. This is a .wrd file I have cut and pasted a few times on a few different forums.
I appologise.
I often forget that this forum is populated by a much more intellectual group who take the time to research what they say as opposed to believeing everything they read on the internet.
I should have taken the time to read through it and brought the statements in the post up to the level expected here. This is a common discussion on many forums and it got to me how underinformed the public is, so I came up with a generally acceptable stock reply.
I appologise.
I often forget that this forum is populated by a much more intellectual group who take the time to research what they say as opposed to believeing everything they read on the internet.
I should have taken the time to read through it and brought the statements in the post up to the level expected here. This is a common discussion on many forums and it got to me how underinformed the public is, so I came up with a generally acceptable stock reply.
In the cold winter, you can run on less octane without having problems.
Quoting from the Gasoline FAQ:
Quoting from the Gasoline FAQ:
New engines with fewer carbon deposits can also run on less octane.
Yes, but does that formula also take into account the oxygenated fuel that we see this time of year?
I've only used 87 octane in my CR-V, but have had it for two seasons of winter, and I notice the mileage go down a couple of clicks during the cold months.
I've only used 87 octane in my CR-V, but have had it for two seasons of winter, and I notice the mileage go down a couple of clicks during the cold months.
Rambling, that is more than a slight difference in the engine
Sandlot:
Good point regarding some of the other sites out there. There seems to be almost no limit on the depth of ignorance from which some folks suffer. . . For my part, I should have added that many engines are NOT programmed to operate as I described in my first post. My wife's Sequoia is one. It's made to run on 87 octane, period, and there's simply no advantage to be had by running higher octane fuel. For such cars, Jill Claybrook and CR are correct -- premium is a waste (unless perhaps some malfunction or dirtyness is causing mild ping...). I got into a forum argument (elsewhere) with one of the folks you described about this issue a couple years ago. Even when I posted a photo of the "87 is OK, but premium is recommended for improved performance" from my O/M, he still angrily refused to accept it. Oh well. . .
Good point regarding some of the other sites out there. There seems to be almost no limit on the depth of ignorance from which some folks suffer. . . For my part, I should have added that many engines are NOT programmed to operate as I described in my first post. My wife's Sequoia is one. It's made to run on 87 octane, period, and there's simply no advantage to be had by running higher octane fuel. For such cars, Jill Claybrook and CR are correct -- premium is a waste (unless perhaps some malfunction or dirtyness is causing mild ping...). I got into a forum argument (elsewhere) with one of the folks you described about this issue a couple years ago. Even when I posted a photo of the "87 is OK, but premium is recommended for improved performance" from my O/M, he still angrily refused to accept it. Oh well. . .
Russell - granted, they are more then slight differences - that part was meant as a joke.
But the manuel stated that the same grade was good for both.
But the manuel stated that the same grade was good for both.
We lived in Las Vegas when we bought our 2nd Isuzu Rodeo, then at 11k miles.
The lowest octane available in Vegas was 87; that's what the book called for as well. Truck ran good, but always pinged like crazy. Dealership never had an answer as to why, except that to use higher octane.
Tried that 3 times, never made a difference. Dealership tried all sorts of stuff, pinging wasn't excessive, but it was there, and shouldn't have been. There are no mountains or steep inclines in Vegas.
We moved back to Colorado with that same 2nd Rodeo, then having acquired 70k miles. Half way through Utah, on the same tank of gas (87) from Vegas, truck immediately stops pinging.
Been here 5yrs now, truck now has 147k miles, still runs on 87 Octane (it KNOW'S if you put in 85) and has yet to ever ping again.
Likewise, this same truck shifts, and runs not so efficiently if you put in 85 or 91 octane's - it's really weird.
Our 1st Rodeo had been bought/raised primarily in Colorado for 4yrs before we moved to Vegas; the manual in that truck said that if you live at high altitude, 85 octane is sufficient. Low altitude run 87 octane.
That's exactly what we did, 85 in Colorado; 87 for the duration in Vegas, think 5yrs or so. We moved back to Colorado when this same truck was about 9yrs old and 150k miles - switched right back to 85 octane without an issue. This truck never pinged a day in it's life.
Go figure.
Slight differences in engine, though, the '91 was a 3.1L Chevy engine; the '97 is a 3.2L SOHC Isuzu engine.
But it's still weird.
The lowest octane available in Vegas was 87; that's what the book called for as well. Truck ran good, but always pinged like crazy. Dealership never had an answer as to why, except that to use higher octane.
Tried that 3 times, never made a difference. Dealership tried all sorts of stuff, pinging wasn't excessive, but it was there, and shouldn't have been. There are no mountains or steep inclines in Vegas.
We moved back to Colorado with that same 2nd Rodeo, then having acquired 70k miles. Half way through Utah, on the same tank of gas (87) from Vegas, truck immediately stops pinging.
Been here 5yrs now, truck now has 147k miles, still runs on 87 Octane (it KNOW'S if you put in 85) and has yet to ever ping again.
Likewise, this same truck shifts, and runs not so efficiently if you put in 85 or 91 octane's - it's really weird.
Our 1st Rodeo had been bought/raised primarily in Colorado for 4yrs before we moved to Vegas; the manual in that truck said that if you live at high altitude, 85 octane is sufficient. Low altitude run 87 octane.
That's exactly what we did, 85 in Colorado; 87 for the duration in Vegas, think 5yrs or so. We moved back to Colorado when this same truck was about 9yrs old and 150k miles - switched right back to 85 octane without an issue. This truck never pinged a day in it's life.
Go figure.
Slight differences in engine, though, the '91 was a 3.1L Chevy engine; the '97 is a 3.2L SOHC Isuzu engine.
But it's still weird.
Saabs (I don't know about other cars) are one good exception where octane number makes a world of difference. In addition to retarding the timing, Saabs also limit boost pressure in an effort to lower the compression ratio.
My 900 had the 87 ok, 91 or higher recommended warning. Now, my 9-5 is a bit more complex w/ "87 okay, 90 (who has 90?) preferred." And then says "in ambient temps higher than 77 a drop in performance MAY be noted with 87."
Saab Trionic is a very interesting ignition system which I believe can make use of higher octane up to 105 maybe?
My 900 had the 87 ok, 91 or higher recommended warning. Now, my 9-5 is a bit more complex w/ "87 okay, 90 (who has 90?) preferred." And then says "in ambient temps higher than 77 a drop in performance MAY be noted with 87."
Saab Trionic is a very interesting ignition system which I believe can make use of higher octane up to 105 maybe?
A couple of years ago, "Car & Driver" magazine tested several cars on a dynamometer. They found that for engines designed for high octane gas, the use of low octane gas reduced power and gas mileage so that the cost savings by the cheaper gas was just about evenly offset. Using high octane gas in an engine designed for 87 resulted on no gains detectable on the dyno instrumentation.
Ken
Ken
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That's my observation in case of my Audi that requires 91 Octane. When using 89 Octane, gas mileage gets dramatially worse. I get about 300 miles on a full tank with mixed city/highway driving on Premium. With Plus (89 Octane), I'm lucky if I get over 200 miles. However, the addition of FP has shown beneficial to the point that I did use 89 octane gas when the gas prices were around $3.25.
Almost all engine design accept 87 with retarded timing to protect itself from the accidental use of 87 (or cheap owner), how much does it retard varies from design to design. That's why it doesn't hurt some models, while it hurts a lot in some others.
Sometimes the amount of retardation and its resulting lost of fuel economy cost you more money than using 91 octane.
Some aftermarket and even manufacture advance the timing even further during the product cycle to "gain" hp for customer. Examples are G35's requirement from 87 acceptable in 2003 to must use 91 in later models, and Hondata's ECU program flash that inprove hp and fuel economy for RSX and TSX.
Sometimes the amount of retardation and its resulting lost of fuel economy cost you more money than using 91 octane.
Some aftermarket and even manufacture advance the timing even further during the product cycle to "gain" hp for customer. Examples are G35's requirement from 87 acceptable in 2003 to must use 91 in later models, and Hondata's ECU program flash that inprove hp and fuel economy for RSX and TSX.
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