Originally posted by sigcrazy7:
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Originally posted by SIGnified:
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Originally posted by jimmy123x:
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Originally posted by SIGnified:
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Originally posted by BB61:
Thanks to both. I’ve been putting ethanol free in my Tacoma for several years. My mileage increased enough to almost cover the increased cost of the gas. I’m sure part of the increased mileage is it has a higher octane level but I’ve always wondered, outside of ethanol, if there are any other differences.
I find frequently that most people rarely understand what an octane rating is much less the value of one.
Unless you using a turbocharger or a high compression engine you don’t require high-octane. It's useful when you need to stop the chances of predetination in the cylinder due to excessive heat from turbo/poor intercoolers and/or high ratio compression which blows before the correct timing aka “knock” (which ain’t the same as run-on).
Most modern cars will dial back/retard timing if you have the wrong fuel for your car re: octane. Many folks think high octane is more powerful, when actually it is less likely to combust (especially under high temps and compression).
In my case I have run 100, 101,108 and 110 octane race gas because my ECU delivers extra fuel to over 20lbs of boost on the K24 twin turbos; even with upgraded intercoolers. Because of this I can run advanced timing too which results in about 550hp. YMMV.
You two are comparing apples and oranges. (I've dealt with both, had a race car 93' Cobra supercharged with 16lbs boost that made 632hp at the rear wheels in the late 90s) and deal with the ethanol free fuel on all of the boats I manage. You're talking about race fuel like VP sells, he's talking about regular gasoline, 90 octane without any ethanol in it. I'm not sure if a Tacoma engine could benefit from 90 octane over 87 when it comes to mileage, but it surely isn't hurting the mileage any.
Ethanol free fuel is usually 90 octane. Not anything but mid grade gasoline you'd find at the pumps prior to 2008. It just has no ethanol in it. It's been proven that 10% ethanol gasoline found at pumps across the country usually nets about a 10% reduction in fuel mileage as well. BUT, also the ethanol is a lot more caustic to the entire fuel system of a vehicle and has a tendency to attract water. (which is why most all of the marina's have recreational 90 no ethanol). On older cars, boats, lawn equipment the E10 fuel found at every gas station will eat right through fuel lines, seals, carberator parts, etc. etc. But the lack of ethanol is most likely to account for the increased mileage.
Jimmy buddy, It is only apples and oranges because I wasn’t referring to anything about ethanol. I only quoted the gentleman before me because he mentioned octane. I was only discussing octane and nothing else. I hope that helps you to understand a little better.
You both are correct, although you are addressing different issues. SIGnified is addressing this statement: "
I’m sure part of the increased mileage is it has a higher octane level". As he stated, octane has nothing to do with increasing your mileage, unless your engine is retarding the timing due to preignition (knocking). IOW, if your engine doesn't require high octane fuels, then using one will not increase your mileage.
Jimmy123x is pointing out that the higher octane fuel that BB61 is using lacks ethanol. Eliminating the lower energy content fuel (alcohol) and replacing it with 100% gasoline is the source of the increased mileage. It just so happens that the ethanol-free fuel is also higher octane, which is not the source of, but a corollary to, the higher mileage in BB61's vehicle.
The short of it: Octane rating is a measure of the resistance of the fuel to self-combust under pressure. Think of it as the inverse of cetane, which is a measure of a fuel's speed of combustion. Gasoline engines compress an air/fuel mixture, so the resistance of a fuel to combust prematurely is paramount, hence it is rated by octane. Diesels, OTOH, only compress air. They inject fuel at the proper time for combustion, so the speed that it takes for the combustion to achieve pressure is most important. Hence, cetane is the method whereby diesel is rated.
But remember, neither octane nor cetane is a measurement of a fuel's energy content, but different measures of fuel's burn characteristics.
