Hi! A few weeks ago, I read in a NG (I don't remember if it is this one, if so, please accept my apologize to bring this issue back!) that cars that toyota recommends to use regular fuel should not use supreme since the octane is too high and the engine would not be able to burn it efficiently, therefore could damage it in the long run.
Is this true? Should it not be true, I have a second question: is it worthwhile to use supreme fuel (does it last longer, is it cleaner, etc.?) or is it a waste of money?
That's BS - the new cars are all computer controlled so spark is advanced/retarted depending on octane/hills/load. You could put aviation gas in it and it wouldn't hurt the engine --- only you're wallet.
On cars built within the last 10 years with EFI and knock sensors, you can run regular fuel when you are driving easy around town, and the engine will knock back the timing to compensate.
Read the wording in the Owner's Manual carefully, it will say something like "For best performance you should run 91/92 Octane Premium, but you can run on 87 Octane if you want, with diminished performance." Not an absolute.
You will get a bit better fuel mileage on Premium because of the slight power boost, but when you consider the price bump for Premium at best it's a wash. Run 89 mid-grade around town if you are worried.
But if you are taking a trip and plan to push for time and go blasting up mountain passes with the car fully loaded, run the good stuff. As soon as the computer notices the lack of knocking, it'll bump the timing and give you that little extra kick in the tuchis.
WARNING: If you have an older car (carbureted or first-generation EFI without the knock sensor and sophisticated fuel and timing control) and they say to run Premium, you run Premium, Period.
The mechanics can only compensate so far for garbage fuel when setting the timing by hand - and if they set the timing while it has Premium in the tank it will be way off if you switch over to Regular. The engine will happily knock hard (called detonation) and beat itself to death when you push hard. And when you punch a hole in a piston or two it's a rather expensive thing to fix.
I had a couple of old Toyota Corollas back in the 70's, they had an external spark adjustment on the distributers, a thumb screw thing you could adjust the timeing by turning it by hand. I think it was called an octane selector or octane adjustment. If the engine pinged or knocked you would turn it and set the timing back a little. If you burned better fuel you could advance the timing settings. Anyway, if you drive easy the cheaper fuel works fine, if you "load" the engine and it knocks or pings then a higher octane rating is needed. The way I drive any more, low octane is all I need. I was doing the math on it, if a person drives 100,000 miles and pays 10 cents extra for higher octane, assuming the car averages 25 MPG it looks they will pay around 4,000 extra in fuel costs. I have a friend with an Accura with over 300,000 miles, he always bought premium, when I pointed out he had probably spent around 13,000 dollars extra by buying premium all those miles he tried regular and it works just fine in the car. I've seen premium at 20 cents over regular at some places in which case you can double the number. Now if you have an engine that requires premium, and you are a hard driver, and there is no spark sensor, buy the premium, I've had some motorcycles that needed the premium but I don't know of any car I ever had that I couldn't use regular and drive normal and get the job done without damaging the engine.
in the owner's book it will suggest/specify the fuel needed. using higher than necessary rating won't hurt. using lower than required could lower the mileage and cause damage. i'd suggest using supreme only if specified. sammm
I did an 'experiment' with my 95 Tercel, and found that I actually paid about $220 LESS using premium fuel, due to the difference in milage from the higher octane fuel.
Based on 10 consecutive tanks each of 87 vs. 93. My '05 V6 4x4 Tacoma is cheapest overall per mile (by a penny) on premium. This is where regular is $3.05, and premium is $3.30.
Have YOU noticed a difference in the mileage? I posted part of a spreadsheet I did her a month or so ago; at 89 Octane @$2.07/gallon, I got
38 MPG; at 93 Octane @$2.17/Gallon I got 44!!! Over the 30,000 I drove that car, as I stated, it cost $220 LESS! And, I didn't have to worry about 'cheap gas' problems.
I'd like to see what it would do now, since I buy gas in Vermont @ lunchtime, and VT doesn't require Ethanol like Mass does, so you're 'supposed' to get better economy with it.
I do notice my LHS requires less and less each fill-up (I fill it every day...like a friend said when I was 16...you fill your car all the time! I said, YOU put $2.00 in every day, I put $2.00 every other day. Yours is sucking fumes, I have a full tank. Guess who's NOT going to get stranded when he's BROKE!!!!
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