Hi all, I have a 2022 1500 with 5.7 Hemi. Many times I now see at the pumps an 88 Octane unleaded with 15% ethanol. It's less expensive than the normal 87 octane. My owner's manual really doesn't address whether or not I can use it without wrecking up the engine in some way. I know it recommends 89, but says 87 can be used for more efficiency. Any definitive answers on the 88? Thanks!
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88 Octane 15% ethanol?
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397STROKER
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the owner's manual also states not to use anything over 15% ethanol. So, you are good to use the 88 Octane with 15% Ethanol. Just don't use Flex fuel, which is 51-85% ethanol.
397STROKER
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Around here the 15% ethanol is only about .04 less per gal. I have run it and it didn't change my gas mileage. I don't think 5% more is enough to make a difference with the added 1 point of octane.
This discussion had me curious. Since octane has nothing to do with energy content, but ethanol ratio absolutely does, I wondered if E88 is going to yield significantly lower MPG. The answer, apparently, is no...
"In a real-world environment, the difference in mileage between Unleaded 88 and regular gasoline is virtually undetectable. Studies by Oak Ridge National Laboratory and the National Renewable Energy Laboratory have shown that with all other things being equal, in a controlled environment, ethanol’s impact on fuel economy would be equal to the loss of energy density. This translates into a loss of less than 2% for Unleaded 88 when compared to regular gasoline. For a vehicle getting 30 mpg this would equate to a drop to around 29.4 mpg, or about the loss of miles to the gallon when vehicle tires are improperly inflated."
So I suppose as long as it's at least a few percentage points cheaper cheaper than the E10 gas you might typically buy, you're still getting your money's worth.
"In a real-world environment, the difference in mileage between Unleaded 88 and regular gasoline is virtually undetectable. Studies by Oak Ridge National Laboratory and the National Renewable Energy Laboratory have shown that with all other things being equal, in a controlled environment, ethanol’s impact on fuel economy would be equal to the loss of energy density. This translates into a loss of less than 2% for Unleaded 88 when compared to regular gasoline. For a vehicle getting 30 mpg this would equate to a drop to around 29.4 mpg, or about the loss of miles to the gallon when vehicle tires are improperly inflated."
So I suppose as long as it's at least a few percentage points cheaper cheaper than the E10 gas you might typically buy, you're still getting your money's worth.
In these trucks it won't at all. In very high mileage ( efficient ) vehicles it does. In my Civic HX, Volt and ELR running non ethanol gave me 5-10 more mpg than 10% ethanol gas.
Yeah, and yours is a more extreme example both in terms of efficiency and the fuel itself (i.e. 10% difference in ethanol content). Here, we're only looking at 5% (E10 87 vs. E15 88).
Well, my real experience says otherwise. My wife's Tucson averages about 30 mpg. Filled it up ONCE with the 15% ethanol, and mileage dropped to 25 mpg. Won't do that again to save 10 cents a gallon.
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One tank isn't a good guage. Need at least three full tank to get an average, and also to allow PCM time to adapt to the different fuel. You also didn't say what fuel you were using before.
Agreed. Even then, it would help to duplicate as many other variables as possible, too…weather, traffic, driving route, etc. Very difficult to do in one shot!
Certainly accurate enough when the mileage drops over 15%. The car has 42,000 miles and this was the first time it was under 28 mpg. That's hundreds of fill ups to set my base number. Was ALWAYS between 28 and 32. Told me all I needed to know. Oh, and I have always used 87 octane.
Darksteel165
Legendary member
How did you expect the truck to re-learn how to burn the fuel on only a single tank?
Wasn't a truck. My wife's Tucson. If it didn't "learn" in 400 miles, I doubt it was going to. It certainly didn't have to learn how to use 87 octane 10% ethanol. Got the same mileage on the first tank as it has on the last.
Darksteel165
Legendary member
Yes it does actually need to learn how to use 87.... You just don't understand how the computers and fuel trim works.
I'm not saying the fuel would of not been terrible, but 1 tank isn't enough at LEAST 2 full tanks even more depending on the car or trucks computer. Same goes with airflow which is why people notice a change on their rams when they disconnect the battery as lots of things go into re-learn mode even the transmission.
Darksteel165
Legendary member
All cars\trucks have a break in time.
You claiming you were getting the same MPG on your very first tank ever is BS.
That's your BS opinion. My statement was based on fact. Since day one, the car has not varied any lower than 28 or any higher than about 32. Except of course when I used the 15% ethanol. Believe it or not, I don't care. I also don't care for some know it all calling me a liar.
Darksteel165
Legendary member
Not calling you a liar, calling you clueless if you think what you are saying is true.
