That’s physically not possible. Even advancing the timing there still isn’t enough energy to do that regardless of the octane rating. Not even close.
No topic is quite like octane rating and what it means and what it does not mean. The lore is deep.
Octane vs mpg again...
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No topic is quite like octane rating and what it means and what it does not mean. The lore is deep.
4WD
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Just curious if you knew. Don't want you putting cheap stuff in your vehicles to find out.
BIL has me curious. 93 is 11% more than 87 right now here and he's saying he's getting 20% better mileage. I've searched around a bit online and can't find anyone documenting that kind of difference. Lots of anecdotal seat of pants observations but no pen on paper hard numbers. I have the same truck and tow a lighter travel trailer. With his numbers I would have saved $90 in gas on this trip we just did by using 93.
Hermann
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A couple weeks ago I filled the Maverick's tank with 91 E0. The tank is probably 85-90% EO now. The 89 E10 was the previous tank. Have driven 432 miles since filling and the DTE is showing 218.
Observations are that the ICE runs smoother and a bit peppier than on 87 or even 89 octane. My dashboard MPG for this tank shows 46.2
This is about 2-3 MPG better than any general purpose tank so far, which includes about 15% higher than the normal amount of 70 MPH interstate. The hand calculated MPG is usually 2 to 2.5 less. This premium is usually 60¢ more than their 87 E10. My grocery rewards more than paid for the difference in the price. I will be filling in a week or so will know more then.
Observations are that the ICE runs smoother and a bit peppier than on 87 or even 89 octane. My dashboard MPG for this tank shows 46.2
This is about 2-3 MPG better than any general purpose tank so far, which includes about 15% higher than the normal amount of 70 MPH interstate. The hand calculated MPG is usually 2 to 2.5 less. This premium is usually 60¢ more than their 87 E10. My grocery rewards more than paid for the difference in the price. I will be filling in a week or so will know more then.
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I believe he could get an improvement in fuel economy that might even be cost-effective. But one data point can't lead to a reliable conclusion. How much data does he have?
My experience hot-shotting travel trailers taught me that fuel economy when towing trailers with large frontal area is very unpredictable due to wind velocity and direction. Towing upwind or crosswind always was worse than towing downwind. And changes in elevation over the course of a tankful had an effect. Mostly the key to long-term minimum fuel cost was to keep speed down. Just because you have the power to climb that 6% grade at 75 mph doesn't mean you should. Or at least you shouldn't complain about fuel cost after you have done so.
Is the 6.6L in his truck flex-fuel? If so, he could run 50% E85/50% 87 and get higher octane than premium at much lower cost. The fuel economy penalty would be acceptable.
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Been common sense in my house for near forty years. Even get better mileage with one brand over another. Those Gen V DI motors make great use of lower octane fuels to where the difference is not as great, if any, in the 5.3 motors for example.
Nope. Would be nice but once the incentives went away, GM quit making them FlexFuel capable.
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Hey Guys, I consider everyone here pretty intelligent. So how can there be any correlation between octane, and mpgs, when octane relates to predetonation? My wife's GM uses 87, so putting 93 91 or 89 is burning money out the tailpipe. Our Toyota product and BMW recommend premium, so 93 is good because 93>91. The BMW states 89 "REQUIRED." Not sure how that could be as parts of the world have only regular from what I hear. But to me, using premium when the vehicle was designed for it means it should achieve the published numbers. mpgs won't go up.
Higher can octane sometimes make a slight difference in running but is not, usually, economically, beneficial. The other aspect of Premium is that it is not as fresh as Regular, because, fewer people run premium. Older gas can have slightly less octane.
$Cost$ per mile goes down by using e85 or a mix of e85 and unleaded is what I get out of this discussion.
Swathdiver,
Can you update this/your 2020 data? I occasionally run a 20-30% mix (E85 & Premium unleaded) in my non-FlexFuel 07 Yukon Denali w/6.2L. Thanks in advance
Can you update this/your 2020 data? I occasionally run a 20-30% mix (E85 & Premium unleaded) in my non-FlexFuel 07 Yukon Denali w/6.2L. Thanks in advance
You have to read the owner's manual carefully. If GM recommends premium fuel, it will get better fuel economy on premium. They have knock monitoring algorithms that advance the spark as long as detonation if not sensed. Any of their engines will run on 87, but fuel economy will suffer because spark is retarded enough that engine efficiency is lost.
That's interesting, Tex.
Excepting the newer DI engines, I have not driven a car in near 40 years where I didn't get better gas mileage using high octane fuel versus low octane fuel. Now, it may not always make financial sense but the cars did perform better on higher octane fuel. There's a difference in economy even between brands of fuel.
If folks would do their own testing, this would not be such a mystery. Most of what you've written is not so. Do some testing if you don't have a DI motor. Well, do some anyway if you do.
Sure Don!
Haven't used a drop of ethanol this year so far. For anyone following, my trucks are fed a steady diet of 93 octane fuel or ethanol, never anything less than 93 unless by accident.
Absolutely a higher octane rating allows timing advance and better fuel economy relative to the fuel content. That's why E85 is reasonably close to the fuel economy of gasoline.
This is true as well but I also have driven cars that were not smart, the timing didn't change but they ran cooler, smoother and got better gas mileage too, back in the carburetor and early fuel injection days.
I'm not that well versed on it, but I've heard that in order to get the most of of it required modifications that would allow for more fuel to be mixed in. But with EFI that can all be done automatically without any mods.
As I noted above the lore is deep on this topic. You cannot and are not accurately measuring fuel economy IRT the octane rating no matter how hard you try. There are standardized tests to measure such things but everyday driving with its myriad of uncontrolled variables is not how it's done.
Hermann
Site Donor 2023
Huh
My latest, it doesn't matter, because it can't be right.
My latest, it doesn't matter, because it can't be right.
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And?
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