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Thread: Premium fuel

  1. #1
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    Premium fuel

    Has anyone compared their mileage with premium vs. regular gasoline? In my Civic Hybrid, I estimate that I get almost 10% better mileage with premium. Of course, the cost difference pretty much cancels out the mileage difference, but I still get a kick out of beating the EPA estimates with premium fuel!

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  3. #2
    Guest

    Premium fuel

    I had a non-hybrid Civic before my Prius. When I put premium in it, I wold get worse milage. I'm told by my mechanic friends that you should only ever put fuel with the recommended octane in a newer car as it messes with the emissions controls and a bunch of other OBD system things that I'll never properly understand. That's great that you're getting better fuel economy though. I wonder how it might improve in my Prius...

  4. #3
    Guest

    Premium fuel

    After reading Rick's and Murray's postings, and after noticing that the price of gas had gone down enough that the price of mid-grade was less than I had paid for "cheap" gas the week before, purely in the interests of science I put $20 worth of middle-grade quasi-premium gas in my 2003 Honda Civic Hybrid.

    My mileage promptly got worse: My daily commute went from 45-47 MPG to 42-44 MPG. I didn't change anything else, and I don't think anything else changed.

    So I'm switching back to "cheap" gas, and hoping my MPG goes back up.

    If it doesn't, I'm coming after you guys.

  5. #4
    Guest

    Premium fuel

    I have always put 89 octane in my non-hybrid cars (Subarus) because I got better gas mileage than with 87 octane gasoline. The increase in gas mileage was about 6-7% while the extra cost was around 5%. 91-93 octane gasoline didn't improve things at all.

    I was thinking of doing the same tests with my '05 Prius, but with the new technology, the "design space" is usually tighter, so I wouldn't think it would make a difference. I have also seen some posts on the newsgroups websites that claim there is no difference.

    If I decide to do the test....I'll let you know.

  6. #5
    Guest

    Premium fuel

    I have always put 89 octane in my non-hybrid cars (Subarus) because I got better gas mileage than with 87 octane gasoline. The increase in gas mileage was about 6-7% while the extra cost was around 5%. 91-93 octane gasoline didn't improve things at all.

    I was thinking of doing the same tests with my '05 Prius, but with the new technology, the "design space" is usually tighter, so I wouldn't think it would make a difference. I have also seen some posts on the newsgroups websites that claim there is no difference.

    If I decide to do the test....I'll let you know.

  7. #6
    Guest

    Premium fuel

    I've tried putting 'premium' fuel in my Prius II for the last couple of tanks. Originally I stuck with the regular fuel from the same company to try and get a good baseline. So far the difference with the premium fuel is less than the variation between tanks on regular - and worse.

    It does not seem to have made much difference. I'll try some other companies versions of premium fuel. With my previous car there while regular fuel was reasonably consistent there seemed to be quite a lot of variation between different companies offerings of premium fuel.

  8. #7
    Guest

    Premium fuel

    Word to the wise, some Prius drivers have put in premium fuel and been rewarded with a Check Engine light.

    The Prius engine seems to thrive on the lowest octane, cheapest fuel you can find. I believe it's because the Atkinson Cycle engine actually does better on fuel that burns faster. With higher octane fuel what you're really paying for is slower combustion. I've seen it claimed that lower octane fuel actually has more energy than premium, it's just that high compression engines are more likely to detonate it. Since the Prius engine is not high-compression (it's high expansion ratio but relatively low compression ratio) this is not an issue.


  9. #8
    Guest

    Premium fuel

    I tried it once as an experiment (long before gas prices went above $3.00/gal), and I noticed a +10MPG difference. But the cost of a fillup to the extra MPG is not worth it. Besides, when you hear of see ads for oil companies' premium gas (BP/Amoco Ultimate, Shell V-Power, etc..), they always say, "for cars that benefit from premium fuels," they are talking about people who own rather wasteful, high-preformance vehicles such as sports cars.

  10. #9
    Guest

    I just put 4 gallons of

    I just put 4 gallons of premium in my Prius. My 41.6 to 42.4 miles per gallon jumped to 46+ A solid slightly over 10% increase. I'll see how the study continues as I use the full 4 gallons.

    [I didn't plan the test, but the gas station was out of regular and I needed fuel.]

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