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Old 11-28-2008, 04:06 PM   #1
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Better mileage with premium gas?

Would mileage increase in a car that normally runs on regular? If so, is it even close to being cost effective?

Sorry if this has been asked before...

, Bill
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Old 11-28-2008, 04:46 PM   #2
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Common question. For most cars, the answer is a resounding "no". Recent information suggests that it could reduce mileage.

Now, while gas is cheap, is a great time to experiment.
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Old 11-28-2008, 04:49 PM   #3
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Generally you will get the best gas mileage by running the lowest possible octane without any knock (knock retard)

-BC
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Old 11-29-2008, 12:28 PM   #4
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Yeah, no more BTU's in premium unleaded vs regular unleaded.
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Old 11-30-2008, 03:56 AM   #5
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Bill,
I did some experiments myself about a year or so ago to answer that same question.
In summary for my car (3.8 V6 , GM sedan , 4L60E trans. ) taken over about 1 , 500 klms ( around 900 or so miles) and mixed driving with some city , some free way / country the results were:

Yes , BUT.
In my experience there IS an advantage but the result is not cost effective.

The fuel economy is around 5% better on premium but the cost is (or was when I did it ) about 7 to 10% more to buy the stuff.
Others may have different results.

Cheers , Pete.
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Old 11-30-2008, 06:44 AM   #6
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In theory you could get a gain in mileage if:

A. When running on 87 octane your knock sensor in your car is sensing sending signals to your engine computer, and your computer is retarding the timing as a result.

B. You build an engine with higher than stock compression, and advance the timing.

In either case the added fuel economy does not pay for itself. The money you spend to get that extra MPG is more than you save.

-Jay
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Old 12-01-2008, 12:33 PM   #7
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..............................In either case the added fuel economy does not pay for itself. The money you spend to get that extra MPG is more than you save.

-Jay
Re:the above comment. My personal experience with the gas prices in where I live suggests that this is very true, even if higher octane can really help some cars get slightly more mpg in some situations. Octane 94 gas is a lot more expensive than regular gas.
Also, I am yet to see higher octane really helps my present cars get noticeably more mpg .
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Old 12-01-2008, 06:32 PM   #8
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I ran an extended test (for a different purpose) in which I ran Regular, Plus, and Premium. My results were similar to Pete's: I appeared to get slightly better mileage on Premium, but it wasn't cost-effective. Plain old Regular works best for me.

Rick
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Old 12-02-2008, 08:57 AM   #9
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Originally Posted by neverendz View Post
Would mileage increase in a car that normally runs on regular? If so, is it even close to being cost effective?

Sorry if this has been asked before...

, Bill
I actually tried this at one time and could not determine more than a very negligable difference, which I attributed to minor variances in wind, traffic, my foot, etc, etc. Nothing really measureable. I was running Sunoco 94 octaine (highest you could get at the time). Cost was a lot more than regular.
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Old 12-03-2008, 06:11 PM   #10
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I umteenth the 'depends on your car but probably negligable and not cost-effective' vote. under certain conditions my cressida gets better mileage with it and slightly more power.
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