Better MPG with higher octane?

[mmondich]

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]

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]

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.

 

[CanRebel]

Ya ill be putting 87 in if from now on. Just sucks since 87 is like 20/30 cents more than 85 here.

Want switch locations?
It cost 30-40 cents more per Liter to go from 87 to 89, where I live.

 

[fishslayer]

so if you had access to a 97 octane you could use that and the ride would be smoother

no it wouldn't... more octane than engine requires achieves zero benefit....in fact ,too high octane could be worse

 

[devildodge]

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]

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]

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]

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.

 

[theblet]

He said he hand calculated

 

[spyder]

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.

 

[Jonsofjons]

Personally on my 5.7l rebel I have noticed a 3mpg when using 89 over 87. Highway driving I use to get near the 20mpg and when using 87 I struggle to get 17mpg. Idk if it’s because I am in the high miles (190k)

 

[23RAM]

I'll do several more tanks in a row of 89 octane

More tanks will help reduce variables in the calculations. It doesn't take long for the computer to adjust to octane changes.
I've tested 89 and found no difference in mileage so I went back to 87. I don't tow heavy, so no need for the extra peak power of 89.

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.

I've been monitoring mine since new and no viable changes detected. Same for my previous two vehicles bought new. I think the misconception of vehicles getting better mileage is based on the fact that your mileage sucks when new because you're breaking it in, driving it more aggressively, having fun, idling while playing with features, etc. Once the newness wears off and you start to just drive it normally, the mileage does increase, because you're not wasting fuel.

 

[mikeru82]

Personally on my 5.7l rebel I have noticed a 3mpg when using 89 over 87. Highway driving I use to get near the 20mpg and when using 87 I struggle to get 17mpg. Idk if it’s because I am in the high miles (190k)

I'm having difficulty believing this claim. I've switched back and forth many times and never noticed any difference in fuel economy. I see more of a difference between winter and summer blended fuel.

 

[Ramfancy]

I think that there are way too many driving condition variables to really calculate exactly how much better the mileage really is using 89 compared to 87. Even hand calculating depends on when the pump clicks off too much to be able to see tiny increases.

The compression in the hemi is such that higher octane is warranted. Yes there is a knock sensor and it will deal with pre ignition, but it does so by changing the timing and reducing performance. Noticeable, maybe…. Especially when towing is the consensus.

Pre ignition is terrible for an engine, that is a fact. From what I understand, the knock sensor only detects knock which means it detects when pre ignition is happening. I will just suck it up and buy 89 to limit any pre ignition. I believe that they only put that 87 is acceptable in the manual so they didn’t lose sales to people who refuse to pay more for gas.

I enjoy the mileage of my hemi compared to my old 4.7 I traded in. I also disagree with people who say if you buy a truck you shouldn’t be worried about mileage. Economy is important, and I dislike spending more money for nothing, but I will admit that I will spend more for 89 octane regardless of any efficiency increases. I believe it is a simple way to decrease engine wear and damage. If I leased, I probably would not spend the extra money on higher octane…

Ironically, had I never read this or other forums, I would probably just be using 87…

 

[Darksteel165]

I've been monitoring mine since new and no viable changes detected. Same for my previous two vehicles bought new. I think the misconception of vehicles getting better mileage is based on the fact that your mileage sucks when new because you're breaking it in, driving it more aggressively, having fun, idling while playing with features, etc. Once the newness wears off and you start to just drive it normally, the mileage does increase, because you're not wasting fuel.

Nope. My 5.7 got better millage after 5k miles on the engine. I put 1800 miles on it the first 3 days I owned it and it was all highway driving getting worse mpg then I even do now.
I also didn't idle in it when it was new, or ever because idling is bad for the engine.
I think the misconception here is you don't know there is a break in time for engines due to all the new metal getting heated and cooled and such.

 

[23RAM]

Nope. My 5.7 got better millage after 5k miles on the engine. I put 1800 miles on it the first 3 days I owned it and it was all highway driving getting worse mpg then I even do now.
I also didn't idle in it when it was new, or ever because idling is bad for the engine.
I think the misconception here is you don't know there is a break in time for engines due to all the new metal getting heated and cooled and such.

Nope? LOL
Idling is bad? LOL
Break-in with all highway miles? LOL
Thanks I needed a good laugh today.

 

[stevj]

My best gas mileage is with ethanol-free gas. I average 4.5 MPG more with it.

Steve

 

[23RAM]

My best gas mileage is with ethanol-free gas. I average 4.5 MPG more with it.

Gas has more energy than ethanol, so you should get a slight bump in mpg and hp with ethanol-free gas. However, around here the only way to get ethanol-free is to buy premium 91+ which is a waste as the engine can't take advantage of anything better than 89. The price difference is also huge at a dollar a gallon more over 87. No thanks.

If I'm towing in the summer long distance, I will put in 89, but since it's my daily driver 99% of the time it's empty and not towing so no need for anything more than 87.

 

[Ramfancy]

I noticed that I seemed to get better mileage as my truck “broke in” for the first few thousand miles. I was told by a tire engineer that the mileage increase as a new truck breaks in is mostly due to the tires breaking in. He said no matter what tire you buy, they have less rolling resistance as they wear. He said it is especially noticeable when they are new. Hard to put amounts on the “break in” mileage increase, but most people agree that the mileage does go up in the first year of driving.

I never get the same tires as replacements so I have never been able to see if the mileage drops and then increases again, but I do not ever remember getting new tires and not having a drop in mileage. I usually get heavier tires though…