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Better MPG with higher octane?

mmondich

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2021 Ram 1500 5.7HEMI eTorque. Has anyone has run 87 octane and noticed a significant change when switching to a higher octane? I know the manual says no lower than 89 but other than MPG potentially being impacted, I don't have any issues. Would possibly spend the extra $$ if I knew it would yield higher MPG's. Thanks.
 

CanRebel

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Soooo after doing some reading and looking around it seems like 85 is a no go. I'm in Colorado and that is the common octane here, does one run the risk of damaging the vehicle if they run 85 or is it just from a performance perspective? I have ran some tanks of 85 and the truck didn't seem to really care and generally its 20-30 cents cheaper. Truck is still new to me and didn't even know it needed a certain octane until reading through here.

Not trying to start an octane war just want to clarify and know if I need to always run 87 or higher. I'm at altitude and read that lower octane is acceptable but want to make sure I'm understanding it correctly.
Technically speaking. You should not use 85.
As Ram Patriot mentioned above. Older cars, yes and at high alt.

Now in real world, is it going to damage your truck? 99% in my view, no.
If you have 85 and you happen to travel to lower alt., then possible. Again, in my view no. Truck is designed to handle it.

I mentioned way above, hot/cold air/pressure are also factors. e.g. you could take 87 gas from location, and drive to another location, and
it would seem your truck isn't performing as well, with same gas. Generally it would be minor though, unless you did some mods on your truck.

The sensors, computers, etc, in engines today, when working correctly are very good.

If I lived where you do, and it was my truck. I would put 87 though. If there happens to be an issue, it could effect your warranty.
 

XmikeX

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Technically speaking. You should not use 85.
As Ram Patriot mentioned above. Older cars, yes and at high alt.

Now in real world, is it going to damage your truck? 99% in my view, no.
If you have 85 and you happen to travel to lower alt., then possible. Again, in my view no. Truck is designed to handle it.

I mentioned way above, hot/cold air/pressure are also factors. e.g. you could take 87 gas from location, and drive to another location, and
it would seem your truck isn't performing as well, with same gas. Generally it would be minor though, unless you did some mods on your truck.

The sensors, computers, etc, in engines today, when working correctly are very good.

If I lived where you do, and it was my truck. I would put 87 though. If there happens to be an issue, it could effect your warranty.
Ya ill be putting 87 in if from now on. Just sucks since 87 is like 20/30 cents more than 85 here.
 

devildodge

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I have been using 88 octane. I got confused with all these fuel threads and gear ratio threads.

So 88 is between 87 and 89.

My 3.73 is between 3.21 and 3.92

I guess I am a betweener.

6.4l Hemi is loving the 88. I drive with the radio on and the windows up...wish I could hear and feel as good as some of you guys.

My engine has 158k miles...I hope I haven't hurt it.

Let's Go Mopar!
 

RAM Patriot

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I have been using 88 octane. I got confused with all these fuel threads and gear ratio threads.

So 88 is between 87 and 89.

My 3.73 is between 3.21 and 3.92

I guess I am a betweener.

6.4l Hemi is loving the 88. I drive with the radio on and the windows up...wish I could hear and feel as good as some of you guys.

My engine has 158k miles...I hope I haven't hurt it.

Let's Go Mopar!
Since you have the 6.4 HEMI engine with a compression ration of 10:1 you should be fine with 88 octane.

The 5.7 HEMI has a compression ratio of 10.5:1 with recommended 89 octane.

Generally, engines with lower compression ratios will safely operate with lower octane fuels. The higher the compression ratios of the engine the higher octane fuels it will require. 🚀
 

spyder

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When I first got my truck, at around 1200 miles on it, I ran it almost empty and filled it with 89 octane. Drove it for 2 tanks worth and hand calculated. Did the same with 87, with almost the same route and driving style, and got nearly 2mpg better with the 87. That makes me think there was something about the driving conditions that made it different, but it also made me not worry too much about which fuel I run.

Once I've got 10k or so on it, I'll try again, but the cost difference and no noticeable performance difference, will likely keep me in 87.
 

HSKR R/T

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When I first got my truck, at around 1200 miles on it, I ran it almost empty and filled it with 89 octane. Drove it for 2 tanks worth and hand calculated. Did the same with 87, with almost the same route and driving style, and got nearly 2mpg better with the 87. That makes me think there was something about the driving conditions that made it different, but it also made me not worry too much about which fuel I run.

Once I've got 10k or so on it, I'll try again, but the cost difference and no noticeable performance difference, will likely keep me in 87.
Two tanks isn't a good average, and need to make sure you hand calculate and not use displayed mileage in dash. Need to do 3-4 tanks to really allow PCM to adjust adaptives and get a good average.
 

spyder

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I'll do several more tanks in a row of 89 octane once there are more miles on it, just to see how it does. Maybe on my spring road trip. Right now, it's getting slightly less than my 2500, so I'm happy enough with it...especially if it increases like so many folks say it will.

I've hand calculated everything, as the computers are notoriously off. I've got 700k miles on Ram trucks in the last bunch of years, and the dash has never once been accurate.
 

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