Electronut
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Am I reading that correctly in the manual? Hemi's always needed minimim 91 octane.
Is this correct? Even for towing a 8k lb. RV?
Is this correct? Even for towing a 8k lb. RV?
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87 Octane is OK for 6.4L Hemi?
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Ionicbrick
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When I had my 2015 6.4 hemi I tried 87 in a couple tanks. I could hear it ping a bit more than usual and it seemed to lag a bit too. So I always fed it 91. However, I towed trailers with it almost all the time… so it could be because I had it working so much.
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I've been running 85 (Colorado) in my 6.4's for years. Most of my usage is towing 8800# TT. Over the years I've tried 87 and 91 and never could tell the difference in power or mileage. I finally drove the truck on a 500+ trip empty, Speeds to 75, most speeds at 65, and over three high mountain passes. Evic read 18.7 but actual mileage was 18.26 I don't think I could beat that with the higher octane.
Electronut
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Could be maybe yours is the older Gen and different engine build? Mine is a 2022.
Wow. Good to know. I'm quite surprised by this. I'm going to try 87.it will be literally my first fill up on fuel. Wonder what the dealer threw in it?
Ionicbrick
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Yup. Could be because it was older. That was my experience, though. I worked that Hemi way too hard since I was towing daily for work, so ordered a Cummins.
Docwagon1776
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6.4 manual calls for 87.
5.7 manual recommends 89 but says 87 is acceptable.
Maybe some of the cars call for 91, but I don't think any of the trucks have.
There was some data logging done on another forum and they did show more aggressive timing with 89 and 91 in the 5.7. It would be interesting to see real time data logging on the 6.4 as well.
silver billet
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If it's recommended to run 89, you'll get peak performance with that octane. My 5.7 hemi pings quite bad on 87, I run 91 when towing and even then I still get the occasional ping.
You do lose HP with the 87 octane as the truck will pull timing which reduces power. So 89/91 doesn't boost power, it's simply the gas you need to get 100% out of your engine because that's how its tuned, 87 is a reduction from that.
Nissan is the only truck I'm aware of which actually lists peak power numbers separately for 87 and 91, something like a 10hp difference IIRC.
You do lose HP with the 87 octane as the truck will pull timing which reduces power. So 89/91 doesn't boost power, it's simply the gas you need to get 100% out of your engine because that's how its tuned, 87 is a reduction from that.
Nissan is the only truck I'm aware of which actually lists peak power numbers separately for 87 and 91, something like a 10hp difference IIRC.
Docwagon1776
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Ford does as well, at least on certain models.
Electronut
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I would agree with you if the manual stated otherwise. In this case it's stating 87 octane. See snapshot right from the manual. My good guess is RAM wouldn't be publishing this for my year/model truck engine if it wasn't good for it. I will definitely see for myself though. RAM can't say jack to me if something goes wrong and that's the main thing. No way they can get out of a potential warranty matter as I went by the book. Just covering my a**.
My 2008 Chrysler Aspen with 5.7L Hemi needs 91 or better. Especially when towing. I have a tuner for it that I can adjust for 87 octane for around town driving to save costs but when towing our TT I put in performance mode and filled with 93 always. 91 very difficult to find in NJ. Whenever I put 87 in it and didn't adjust engine timing with tuner I would hear it knock.
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silver billet
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Interesting, is this one of those year specific things where they change their mind on the octane (see engine oil on the 5.7 hemi for example, it's all over the map)?
That's actually kind of nice if you get that rated power at 87.
mwalsh9152
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87 is fine. I have tried higher octanes a few times, but there was no noticeable difference in performance, or fuel mileage.
Crusty old shellback
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Go on youtube and watch the engine masters episode on gas octane ratings. You will be surprised.
All the higher octane does is prevent detonation more than lower octane does. It's mostly for higher compression engines, like 12:1 and higher.
Your not going to notice any difference in our trucks by using a higher than recommended octane gas. But if it makes you feel better to spend the extra money, then go ahead.
I had to run 91 in a Blown 383 stroker motor because at boost, the motor would ping on anything less. motor had a 8.75:1 CR and was running about 8 PSI of boost.
All the higher octane does is prevent detonation more than lower octane does. It's mostly for higher compression engines, like 12:1 and higher.
Your not going to notice any difference in our trucks by using a higher than recommended octane gas. But if it makes you feel better to spend the extra money, then go ahead.
I had to run 91 in a Blown 383 stroker motor because at boost, the motor would ping on anything less. motor had a 8.75:1 CR and was running about 8 PSI of boost.
same as my 2020 says and I have used 87,89 and 91 just see if I could detect a difference and nada iota of difference in seat of the pants or mpg. I suppose if I were pulling heavy in really hot weather in mountains I might go 91 just because but running empty I have driven to Moab in early July from Montana and back without any issues running 87.
my new Mazda cx5 turbo lists 87 at 227 hp/310 ft/lbs on 87 and 256 hp/320ft/lbs on 93 but shows dyno graphs showing the lines match until 4000 rpms where the 93 numbers carry out just a bit further. their engineers say for normal driving there is no benefit of running higher than 87. I have been doing my best tho to visit 6000rpms whenever possible
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Electronut
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Not sure if either of you pull TT and/or 5th wheel RV, but would still be applicable to use 87 octane if so? I'm assuming good to go and no noticeable performance difference or necessity to go higher octane when towing.
Does 89 gas last longer than 87?
https://www.youtube.com/watch?v=c1ssA8L6-t8 The answer is typically "no". 89 octane gas generally does not last any longer than 87 octane gas. This is because both octanes are composed of the same components and follow the same refining
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how long is your truck sitting? from everything I have read it takes at least 3 months for
Picked the truck up in January of 21 and only have around 5,400 miles on it….. I have quite a few antique tractors that I only run once in a while that used to constantly foul plugs on until I switched to 89 in them, haven’t had a problem since. So I just figured if I keep the 50 gallon tank full of 89 on the truck and it happens to sit for a few months I’ll be good to go…Does 89 gas last longer than 87?
https://www.youtube.com/watch?v=c1ssA8L6-t8 The answer is typically "no". 89 octane gas generally does not last any longer than 87 octane gas. This is because both octanes are composed of the same components and follow the same refining
how long is your truck sitting? from everything I have read it takes at least 3 months for
Electronut
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Noone should keep any gas sitting in the tank of any vehicle longer than 3 months unless treated with some form of fuel stabilizer which I do since my vehicles sit a while too. I always use Startron to preserve fuel and when I want to remove carbon buildup and clean up the fuel system I also use Seafoam.
Doesn't matter what octane you use because ethanol is your enemy.
Doesn't matter what octane you use because ethanol is your enemy.