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I usually buy the 87 octane gas but yesterday the pump had the same price on the 89 octane so I put that in. Can I expect better mileage? Normally that price is a few cents higher. Is it worth putting in the 89 all the time?
No, not unless your engine truly requires higher octane gasoline for the timing of the engine. most engines, even cars that say "recommended" in the manual, do not benefit from higher octane gasoline.
If you car called for mid grade you wouldn't see a gain in millage using premium.
If your car calls for mid or premium and you use a lower grade your millage will suffer.
Quote:
Originally Posted by DCforever
That's not quite true. Electronic ignitions can change the spark advance based upon fuel performance. I get slightly poorer mileage on mid grade gas than premium.
About 30 years ago, the Federal Gov't required all vehicle engines to run on 87 octane. 89 and 91 are refined for the few vehicles that need it. Using higher octane in a 87 engine will not improve the mileage or make the engine run any better. You are throwing away 10 and 20 cents more a gallon for nothing. But if you have an engine that requires a higher octane, it must be used. And gasoline is gasoline no matter what brand you use. [unless it contains ethanol] It all comes from the same tank farm.
Yep;to get the benfit you need to increase compression which is what they did after WWII to burn the higher octane from plant conversion to producee it for war effort. Octane is the burn rate and today they have EGR system that do preetty much teh same thing to stop valve flooding .
Poor 91 with some 10w30 oil mixed in. No more than a quart. If you put to much than it gunks up your valves. The added oil will lubricate your pistons and cause less friction thus giving you better gas mileage.
Poor 91 with some 10w30 oil mixed in. No more than a quart. If you put to much than it gunks up your valves. The added oil will lubricate your pistons and cause less friction thus giving you better gas mileage.
That may work with a chainsaw engine, or maybe a lawnmower, but in a modern automobile that will most likely cause you car to smoke, will produce no tangible benefits, and may cause an expensive repair.
Yes, ethanol has a lower energy density than gasoline, so a given volume will not move the vehicle quite as far as the same volume of gasoline. The blend is sold as part of a strategy to use less foreign oil.
Tha would be simplistic and often wrong. It depends upon the car.
No, it isn't simplistic and often wrong. Obviously, anyone reading the question should know that the context of the question was in consideration of the car's design and manufacturers recommendations.
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