87 vs 91 (or 92) Octane?
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.
Now, what do you think, and why?
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.
Now, what do you think, and why?
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You can usually hear if you're getting detonation (a pinging / knocking noise). If you notice this while running hard, you may want to spend the extra $ on higher octane.
However, with the modern engine management systems, most (or all) cars designed to run on higher octane gas can run on a lower octane with diminished performance but no damage.
The question is, do some (or even all) cars designed to run on the lower octane gas have the capacity to benefit from a higher octane? If some but not all, which ones have this capacity? Finally, if such cars exist, how do they differ from the ones designed to run on a higher octane gas but able to use the lower octane gas?
2009 BMW 335i, 2003 Corvette cnv. (RIP 2001 Jaguar XK8 cnv and 1985 MB 380SE [the best of the lot])
I do know that using lower octane in a Mercedes can cause damage. When I had one, a '94 C280, I heard a service guy explain that to a customer, showing her a carbon-encrusted internal engine part he kept on his counter.
Someone, please watch the video: http://www.europeancarweb.com/tech/proven/epcp_1007_2010_volkwagen_jetta_proven/- - viewall.html
Just copy and paste it to go to that location.
2009 BMW 335i, 2003 Corvette cnv. (RIP 2001 Jaguar XK8 cnv and 1985 MB 380SE [the best of the lot])
Sorry, yes, I see the point in your last para of Reply 3, and I forgot it was only text and graphs. I know the 5-cylinder VW engine isn't a barnburner - even my Fit has a better 0-60 time - so maybe it's the sort of under-stressed engine that would benefit from higher octane.
I bet a lot of people won't accept that there would be any improvement to engines specified for 87. In fact, I'm still on the fence.
Today, I ran my Fit hard in the mountains starting with a full tank 50% 91. It felt great but it always does. Now I'll run it to near empty, fill up with 91, and get a seat of the pants impression.
In the other direction, I special-ordered new a '99 Z28 that I still have. The manual specifically says it's ok to use 87 with lower h.p. I phoned the GM techs to be sure. Since I don't need all that h.p., I've been using 87 in it for years, getting 30.2 mpg door to door San Diego-Indianapolis-San Diego because sixth gear is 1,750 at 75 mph. Engine is in great shape with about 65k miles. But if the manual required premium gas, I'd never use regular.
For instance, my 05 Passat with the 1.8T requires a minimum of 91. Around here, 93 is common so that's what I use. If I were to run 89 or lower, the computer would compensate for that which results in lower MPG.
My 00 Odyssey states in the manual that if one were to use 91 isntead of the recommended 87, the HP will increase from 200 to 205. I've used premium a few times in the van and to be perfectly honest, I couldn't feel the difference.
IIRC, C&D did an article on this a few years ago in which they did their road and dyno tests to see if there was a benefit of using premium in vehicles rated for regular. The results were there was not a benefit.
Not going to use regular even if the car might somehow compensate for it. "Only" means something, especially to finicky engineers.
Old car gets the good stuff too, even if I am tempted to run my homemade gasoline-benzol-alcohol mixture :shades:
I never buy it, but it's available. Maybe because of the boaters though.
Regards:
Oldengineer
I started this thread with the link to the objective study using a dynamometer and the 5-cylinder VW engine. You are the first to confirm what I think I'm seeing - more power and better mileage, in my case with a 2011 Honda Fit Sport 5mt on 91 octane - and corroborating the premise. I'd have to revert to 87 octane to see whether the mpg meter drops back, because my engine is still pretty new at 4,000 miles, and break-in might be a factor.
I plan to write a letter to the editor of Car & Driver magazine on this subject because they published the first article I've seen that recognized the Fit's sports driving merits, surprising them with its result in the emergency lane change test, going 6 mph faster than any other car including Ferrari F430, Corvette Z06, etc. Am hoping they'll explore both the 87 vs higher octane question, and the stock Fit as a GT performer on twisty roads. A race-prepared Fit (with stock engine and transmission) has already proven itself on the race track, e.g., in the 2010 25 hour Thunderhill race where the C&D entry placed 15th overall, lapping at 83 mph. I put 17-inch Kosei Racing wheels with 215/45 Kumho SPT's (left over from an '04 Civic) on mine, and run very well with real sports cars on San Diego East County's great winding two-lane mountain roads. Am hoping C&D will explore this aspect of sport driving the stock Fit, possibly enhanced by the 91 octane theory. It would be valuable to see whether they can also confirm the theory by a dynamometer.
Regards:
Oldengineer
Does the added mpg offset the added expense of premium though?
Does it make a difference during in-town driving?
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).
If you can show actual results in a controlled environment, they'll I'll start to believe.
BTW, my Passat requires premium. I paid a 12% premium for it today.
No data show that engines designed strictly for regular run better or longer on premium. "
Why use premium gas when regular will do?USA Today)
To quote Mr. Shiftright, premium gas is not a doggie treat for your car.
2. No one is suggesting to use regular where premium is specified, just the opposite.
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%.
#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.
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.
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.
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?
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).
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.
Are you sure its the octane level? I think a lot of premium fuel doesn't contain ethanol.
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.
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."
In town, the car seems peppier as I noted, low end torque feels slightly better, and the hesitation is gone.
Regards:
Oldbearcat
Regards:
Oldbearcat
I got the email address to send an email to the editors of C&D, and started a draft.
Regards,
AndySD
"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.
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.
Here's a text only cached version that may stick around for a while.
Car and Driver has looked at this before btw. Back in '01 they said "only a few vehicles calibrated for regular fuel can advance timing beyond their nominal ideal setting when burning premium." Performance gains were minimal (or negative in the case of an Accord in their fleet). Regular or Premium?
If you're still composing your note to C&D, you can ask them if their story still holds true with your higher combustion Fit engine.
Yes, I'll reference the '01 C&D test, but we're getting current real life evidence from your forum contributors that it does help, just like the recent subject test concluded.
Regarding the V-6 Honda in the '01 C&D test, "The Accord took a tiny step backward in power (minus 2.6 percent) and performance (minus 1.5 percent) on premium fuel, a phenomenon for which none of the experts we consulted could offer an explanation except to posit that the results may fall within normal test-to-test variability."
I like the text version although it doesn't have the graphs.
From the recent European Car magazine test, the h.p. gain on the lowly base 2.5 liter 5-cylinder VW engine increased from 138 to 145! That's 5 per cent. And:
Conclusion
Does higher octane fuel make a difference on all vehicles? It did in this case. Because of VW's advanced electronics and highly adaptive engine management, the Jetta 2.5L has an elastic response to a changes in octane levels. Once we put in the 87 octane, we could feel the drop in performance - less responsive, less peppy, and overall just different. The engine instantly detected the reduced octane levels and adapted for standard performance. This analysis was based on more than 1,200 miles of driving over a week.
Switching between the two octanes allowed us to use the dyno to detect and confirm or refute any driving subtleties we noticed during the week. Even though the Jetta's gas tank flap advises 87 octane, the dyno graphs clearly show that running premium gasoline does have performance benefits including, a slight increase in fuel economy. In the end, you get what you pay for. If you want standard performance use standard gasoline. But if you want premium performance, pay for premium gas.
That's a red flag for me and it really indicative of the placebo effect. I put premium gas in my car, so it must be running better. Back in the day, when I got a new pair of sneakers, I could run so fast I'd challenge my older brother to a foot race. Never beat him.
Testers should stick to repeatable results, not seat of the pants stuff.
Road and Track says "There's no benefit in octane higher than the recommended one (as systems generally adjust downward in response to knock, not upward until they hear it)."
Fun stuff, got any more links anyone?
However, I am going to continue my personal test with my 2011 Honda Fit, to calculate mpg using 91 for comparison, and to write C&D to see if they'll do a test to confirm or refute the recent European Car mag test. I'll also refer to C&D's own 2001 test.
If I were a car commuter where fuel cost were an economic consideration, I wouldn't think for a moment of using premium (unless unexpected reports come from this forum of more economy with premium).
I do hope others will run comparative mpg tests, and advise this forum.
Just a personal decision, but I'm also going to continue to evaluate the seat of the pants indication that my Fit is more powerful. I drive this car in such a way that paying a little more for gas would be worth it to me. On many weekends, with other real sports cars, we push the mountain road curves. With no desire to collect speeding tickets, we do not drive at high speed on the straights.
I believe the contributors who say their cars run smoother on premium, that it applies to certain engines. The literature indicates that high mileage cars do run smoother on premium due to build-up of carbon on the pistons and cylinders, effectively raising the compression ratio.
Our 2011 Accord SE is so smooth, though, and I wouldn't use more horsepower if I had it, so I don't see any reason to even try 91 in it.
I also have a '99 Camaro Z28 I special-ordered new 13 years ago, in which I've used regular gas almost all its life. It runs fine on regular, which is permitted by the owner's manual, and I don't have any need or desire for the full 305 h.p.
Well, some people run a higher octane just for that reason - they report getting better mileage. But the price differential has to be just right; usually that's a dime but it varies a lot.
For the same reason, some people run the ethanol free stuff if they can find it, because their gas logs show the extra cost of the gas is made up by the higher mpg.
I had a Fit Sport for a weekend and it seemed peppy enough. On my test drive of the Fit automatic, it was such a dog with three people in it that I'd want to switch to premium, Techron, Heet, aviation gas, vodka - anything to get it where it could merge on the freeway. :shades:
The second gen Fit like mine has a little more h.p. at 117, and with the manual transmission feels pretty strong. You can't be afraid to wind it up to 7,000 max rpm where it is still very smooth. Really a fun car. I have 17" wheels and 215/45 Kumho SPT sport tires. I didn't buy the wheels/tires for the Fit, but had them in the garage for 7 years from a weak moment of buying for an '04 Civic I had at the time.
Maybe we'll get back out that way some day and we can meet for coffee at the Hob Nob Hill and compare gas logs (my wife is from La Mesa but all her relatives moved, durn it)
You're right about those five ethanol-free gas stations in CA. I reported them a few days ago, and forgot about them, because I've read ethanol is in all gas in CA, which is what the reference says that I pasted below.
Ethanol in gasoline seems to be a complicated and controversial issue, dangerous for boats with fiberglass tanks - but boaters with gasoline engines have no choice except to replace their fuel tanks with stainless steel. Here's a reference:
Ethanol Free Premium Unleaded Gasoline Coalition
California Is Not A Mandatory Ethanol State
But It Might As Well Be
California does not have a mandatory ethanol blending law, but it should because ethanol is already in all of the gasoline in the state. The California Air Resources Board has an agreement with the EPA to blend ethanol into all of the gasoline in California at the 5.7% level. That level has been changed by a California law that allows the distributors to go to E10 by 2010 and they surely will for the economic benefit to them. It is unfortunate that the greedy ethanol companies and the oil companies pay no attention to the known problems with ethanol in gasoline. There are no exemptions in the California agreement and no requirement for labeling pumps, so you get problems like this.
Prohibit Ethanol Blending In All Premium Unleaded Gasoline
Every mandatory E10 state has exemptions to their blending law, because there are a number of piston engine applications that should not, and some that cannot, use ethanol blended gasoline. Unfortunately the exemptions are not uniform. They vary from only one exemption in Washington, aircraft, to a universal exemption of premium unleaded in Missouri. All states exempt aircraft usage, but most states like Oregon and Washington make it almost impossible to get unblended gasoline. Oregon is the only state that allows for unblended regular and premium gasoline for the exemptions, and then makes it almost impossible to get any unblended gasoline. All other mandatory ethanol states just allow clear premium unleaded gasoline for the exempted classes.
The following piston engine applications should not use ethanol blended gasoline:
Any 2 cycle engine used in tools, watercraft, snowmobiles, etc., or small 4 cycle engines.
Any engines used in an emergency stationary engine application like a generator or a pump, especially in a humid climate.
All watercraft. Ethanol blended gasoline should never be used in a marine environment.
Antique and classic cars and classic motorcycles.
All aircraft.
All of these users must be able to get ethanol free (E0) gasoline. If you live in a state without a mandatory ethanol blending law, you have no exemptions, ethanol will eventually be blended into all of your unleaded gasoline and there is no requirement in EISA 2007 to label gas pumps with ethanol content.