A friend of mine, who is a rather intelligent guy, tells me he gets better mileage in his truck when he uses 91 vs. 87 octane gas. So, I figured I'd try a tank or two of premium to see. I haven't had any conclusive results yet. I wanted to know if any of you think 91 is better for any reason really, not just mileage. The car seems to be happier on 91. With gas prices as ridiculous as they are, the extra $0.20 is almost nothing. SO yeah, whatdya think?

Thanks!

Been wrestling with this myself. I'm just not smart enough to figure out mathematical "word problems". I get around 1 mpg more on Super as opposed to mid-grade, which is of course 10 cents more per gallon.

VM

If you drive 300 miles this is what you get:

15mpg @ 300mi. = 20gal. @ 2.999= $59.98 (super)

14mpg @ 300mi. = 21.4gal. @ 2.899= $62.04 (mid grade)

So at driving 300 miles you would save $2.06 by buying super and getting an extra 1mpg. I drive a 18wheeler for a living, so a 1mpg increase can save me alot of money. But you have to look at it long term, how much will I save in a month? or save in a year? If you do not do alot of driving then you have to decide is it worth it. To be worth it you have to get that extra 1 mpg every time. What I have been told is that you do not need super unless it is required by the manufacture or you have increased your compression.

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87 D-100 /6

the only reason you'd get better economy from 'better' gas would be if you tinkered with the timing a little when you put in the better gas...that would probably entail MORE than just adjusting the position of the dist., more likely a recurve to really make it worth the time and $$.

sb

For a late car, this can help assuming the car doesn't like the quality of the regular and rings in all the advance since the knock sensor is going nuts with the crappy gas...

For our carbed cars, this would entail a recurve or better compression.

When Super and Regular were about 10 cents apart at Costco I'd dial an extra 2 degrees of highway advance in and be able to save a couple bux per tank (like $2 tops) using super...now that it's a 30 cent difference...I find it economical to detune the curve a bit, change my carbing slightly, and drive sanely - still peppy and gets fair gas mileage- won't win a drag race, but I'm not out an arm and a leg for gas...

-D.Idiot

The only time *just* switching to premium will save fuel is with a computer-controlled engine where the knock sensor is holding the timing back with regular or mid-grade fuel.

With a carbureted car and no computer, you might be able to re-tune the engine to get better mileage by advancing the igniton timing and leaning out the mixture, but then it'll ping like crazy if you were to go back to regular. And the difference will be fairly small in most cases.

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