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87 vs 91 (or 92) Octane?

24

Comments

  • andysdandysd Posts: 87
    I agree you are quoting the prevalent viewpoint, but contrary to your statement, there are data that indicate differently. Please read my original posting, and check out the referenced link:

    #1 of 21 87 vs 91 (or 92) Octane? by andysd
    Nov 25, 2011 (1:23 pm)
    I've always believed that if 87 octane is specified by the manufacturer, then you're wasting money to use 91 or higher. However, recently a friend sent me the following link regarding a serious test using a dynamometer that indicates otherwise.

    http://www.europeancarweb.com/tech/proven/epcp_1007_2010_volkwagen_jetta_proven/- - viewall.html

    I sometimes drive my 2011 Honda Fit Sport 5M really hard on nearby twisty mountain roads, constantly accelerating (with all its mighty 117 horses) to red line. So I plan to put in a couple of tankfuls of 91 octane (as high as it gets around here), to see if I can feel a difference.
  • steverstever YooperlandPosts: 40,022
    edited December 2011
    I remember the first post. :shades:

    Dyno results are more persuasive than seat of the pants stuff. Even then, the linked results aren't spectacular by any means, nor will real world conditions mimic the dyno test conditions very often. We're talking peak power gain of 7 hp @ 5790 rpm and peak torque gain of 13 lb-ft @ 4150 rpm. The torque number is interesting, but the HP number at those rpms is practically a rounding error. I'm not sure how they got 7 hp subtracting 133 from 138 for test 1 either. :shades:

    So I want to see your dyno numbers. :)

    Btw, that link of yours breaks, probably because of the dashes - here it is for those wanting to see it.

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  • robr2robr2 BostonPosts: 7,744
    3. How could you pay a 12% premium? I just checked Californiagasprices.com which shows $3.29 avg low price for regular, mostly at Arco, and $3.49 for premium. that's a difference of 6%.

    I pulled into a Mobil today here in Boston. 87 was priced at $3.45 and 93 was priced at $3.85. That's 11.59% more.

    Although the price spread typically is only $0.20 between 87 and 93, I've noticed more stations jacking up 93 by more. I think it's because the stations understand that some buyers have to use premium whereas folks like you can switch to regular without any issues.
  • robr2robr2 BostonPosts: 7,744
    Btw, that link of yours breaks, probably because of the dashes - here it is for those wanting to see it.

    I followed that link and read the story. There is a mention of a $300 intake in the middle of it without reference to the story. Does this have anything to do with it?
  • andysdandysd Posts: 87
    At least in the San Diego area, 91 is the highest generally available. There must be cars like yours around here. Are you sure your owner manual's requirement won't be satisfied with 91 if that's available in your area?
  • andysdandysd Posts: 87
    I'm sure you can interpret the intake question as well as I. Am going to try to spend less time on this, and try to write C&D about their doing the test including dyno we all want.
  • steverstever YooperlandPosts: 40,022
    As I read it, they put the intake on to further increase the hp and torque and called it Test 2.

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  • andysdandysd Posts: 87
    You mention compression ratio as a possible factor. I agree, and in reply to someone else who touched on c.r., I replied:

    Dec 14, 2011 (9:42 am)
    Consensus seems to be growing! Another believer.

    Three of us have seen indication of about 10% improvement in fuel mileage. Californiagasprices.com indicates a 6% difference in gas prices, so a 10% improvement in mpg definitely would pay off. Then there's the bonus of the indicated tractability improvement at lower rpm - that sort of relates to your question about in-city driving.

    I was considering putting premium in my 2011 Honda Accord SE, but I have no interest in more horsepower, and it runs so smoothly on regular, that I haven't so far. However, in the interest of science, maybe I will - if only to see if economy is improved. Yesterday's fill-up showed 25.5 mpg with primarily city driving.

    Oldengineer brought out the relationship between compression ratio and likelihood of benefit. Before I started this thread, I emailed back to the friend who first sent me the link about the European test,

    "It might make even more difference on the SV [my Suzuki SV650 motorcycle], which has a high compression ratio of 11.5.

    "The Fit's is 10.4, and the Jetta 2.5 L's is 9.5, so it might benefit the Fit more than the Jetta, because the Fit might be closer to pinging."

    I hope C&D will take up an accountable study of the matter (if I ever get around to writing them).
  • robr2robr2 BostonPosts: 7,744
    At least in the San Diego area, 91 is the highest generally available. There must be cars like yours around here. Are you sure your owner manual's requirement won't be satisfied with 91 if that's available in your area?

    My VW will run on 91 but it's not readily available in the northeast. The only brand that offers it is Sunoco and there's only one that I know of.

    Around here it's 87, 89 and 93.
  • andysdandysd Posts: 87
    I get you. Too bad. Better move to SD; the weather's better, too.
  • robr2robr2 BostonPosts: 7,744
    Been there - was kind of bored with the weather. I like real seasons with snow and leaves and rain and cold and hot and humid.
  • berriberri Posts: 4,142
    Three of us have seen indication of about 10% improvement in fuel mileage

    Are you sure its the octane level? I think a lot of premium fuel doesn't contain ethanol.
  • andysdandysd Posts: 87
    Good point, but in CA ethanol is unavoidable. See a quote:

    ETHANOL CONTENT IN CALIFORNIA'S GASOLINE INCREASES TO E10
    POSTED: MAR 05, 2010

    Since the ban of MTBE in California, the state has used a 5.7% blend of ethanol instead of the E10 more common across the rest of the country. But today California is switching over to the 10% blend. This is good news for consumers who can now use a higher content of renewable fuel and for America's ethanol producers who have a newly expanded market - but questions remain about the future of ethanol use in California as the state's low carbon fuel standard moves toward implementation. As written, corn-based ethanol may not qualify as a low-carbon fuel because the state insists on charging it with additional penalties for "indirect effects," as opposed to only the "direct effects" charged to other fuels.
  • andysdandysd Posts: 87
    I hear you, but after about 17 years in and around NYC/Roslyn/Tarrytown, 3 years in the Navy, 5 years near the beach in Lomita CA, 11 years in Holland (still have the same ex-Dutch wife), 20 years in Saudi Arabia, a couple of years in Houston, a year in Calgary, we chose Socal in sight of the Pacific for retirement 27 years ago.

    You probably wouldn't believe all the things we can do, e.g., within 20 minutes of twisty two-lane mountain and desert roads, that I enjoy every weekend on two and four wheels with fellow enthusiasts. We go over Mt Laguna's 6,000 feet almost every week where there is plenty of climate change, colored leaves, sign "Against the law to throw snowballs at vehicles."
  • Whether I fill the CRV up with premium fuel or not depends on the price spread between the fuels. For a good while here, the price differential was too much to make it worthwhile.

    In town, the car seems peppier as I noted, low end torque feels slightly better, and the hesitation is gone.

    Regards:
    Oldbearcat
  • The best verification I have is that I make a 500 mile roundtrip to Pittsburgh once a month for business. I've used both fuels for a bunch of trips, and, the CRV consistently does better on premium gas. The best the car's ever done - I filled her up with premium outside of Atlantic City, NJ, and got 34.5 MPG running her 70 - 73 MPH on cruise - headed for home in WV. I suspect the gas I bought didn't have any ethanol in it, and, it's not available in my state. My CRV is a 2wd by the way.

    Regards:
    Oldbearcat
  • steverstever YooperlandPosts: 40,022
    edited December 2011
    There are ~8 "pure gas" stations in WV (assuming the list is current). Not a lot.

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  • andysdandysd Posts: 87
    That's good data. For comparison, can you say what your mpg is for the same trip using 87 gas? What octane was the premium you used? The (current) CR-V engine has a compression ratio of 10.5, pretty high, possibly leading to the conclusion that higher c.r. engines (specifying 87 octane) benefit relatively more from octane higher than 87.

    I got the email address to send an email to the editors of C&D, and started a draft.

    Regards,
    AndySD
  • steverstever YooperlandPosts: 40,022
    "But what if you don't have a high performance vehicle? Will putting high octane premium gas in your car make it run any better? Well, mechanics say it could actually make your car run worse.

    "They have sensors on what the combustibility rate is in the pistons and stuff, and it will screw up the sensors because the rate is slower than what regular gas fires at higher combustibility rates," said Fox Negaunee sales associate, Casey Massie."

    Premium vs. regular gas, what's the difference? (FoxUP)

    The comments there run the same gamut as here. :D

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  • andysdandysd Posts: 87
    edited December 2011
    It's great that our Host, Steve, is contributing his ideas and info from links. Thank you, Steve. By the way, we need your help again if you can make that original link available. The way I pasted it in Msg #1 now goes to a subscription page for European Car! It worked for a while.

    As to the question, "But what if you don't have a high performance vehicle? Will putting high octane premium gas in your car make it run any better?"

    As a preliminary answer, none of the vehicles belonging to contributors to this thread are high performance vehicles, and they are reporting benefits. The car in the test that started this off, in Msg #1, is a VW Passat with the base Golf engine, the 2.5 5-cylinder. Mine is a Honda Fit. Oldengineer's is a Honda CR-V. Another is a "VW."

    I'm not trying to push my personal idea, but instead am trying to go further with the test that reported benefit in the link referenced in Msg #1, and so far we are seeing real life evidence that there is benefit.
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