Quote:
Originally Posted by Texas Coyote
I am sure that there are people that will vehemently flame me for saying so, but yes..... Get out the owners manual turn to page 132 and see if it says to use 87 octane, or if it doesn't say "87 octane or higher". .... The same people that complain about the performance of their cars are using regular grade fuel and in some cases non synthetic or heavier than the recommended 5-20 wt oil..... I fill my car to the top to accurately check my fuel mileage and always average over 37 MPG unless I am driving fast and hard in city traffic. I am only getting around 33 at the moment because I am having too much fun with my new super charger but once I can control my impulsiveness I think I will be bringing it back up closer to what I was getting.... If you are now using regular,smell the oil dip stick and you will find that it smells like gasoline., that is because when the timing is retarded the fuel doesn't completely burn and gets into the oil by washing down the cylinder walls and causes premature wearing or the walls and rings...... Be kind to your ass for it bears you.
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The mpg depends on how much energy is produced when the fuel-air mixure burns. Most, but not all the time, more energy producing compounds like toluene are in greater concentrations in premium fuels but not always. Ethanol has much lower combustion energy so it really isn't a benefit. MPG drops when its used..
Ethanol can be an octane booster but the combustion energy of ethanol is much lower than typical gasoline; worse, it costs more energy to produce ethanol than gasoline and wouldn't be used at all if it weren't for government subsidies. So the use of ethanol is limited.
As for retarded timing, that doesn't happen in FI systems with computer control. When slowing the fuel injectors are cut off so no fuel reaches the combustion chamber til you get close to idle speed. Til then the firing. So when you slow down do it in gear, not with engine idling. And in any case the spark advance matches the rpm curve regardless whether the engine has fuel-air mixture in the comnbustion chamber.
And little if any gas gets washed into the oil sump unless your rings are really bad or the fuel flow is very poorly regulated.
Again, its virtually always uneconomical to use higher grade gas than necessary. An energy booster, like most injector cleaners, will help but again not economical. Its use is strictly keeping passages clean.