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Octane Level for 2020 RAM 2500

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psardac7

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Hello:
What is the consensus on Octane Level, 6.4L Heavy Duty V8 Hemi. Daily driver + part time towing 6,000 lb bumper pull travel trailer.
Owners manual states 85 with a TOP TIER Detergent. Use 85 then maybe a higher level while towing?

thanks....Pete.......
 
Couple threads exist on this. My recollection is most people stick to 87-89. I believe the manual says 89 or something. There is a recommendation.

I ram 87 for first few months. Then switched to 89 and noticed a little better mpg. Price is negligible around here so I maintained it. I occasionally tow 10k+ and figure running 89 is a good middle ground for getting what I can get. Most people agree throwing 93 in right before towing won't produce real results like you expect. For the most part. Don't put in bad gas and drive it.
 
The octane number in fuel is simply a resistance to detonation. Marketing names like "mid grade" and "premium" are just that, marketing. It's not any cleaner or pure. The compression ratio and timing of an engine will dictate what octane it needs to resist knock (pre-detonation of fuel). Altitude and the lack of oxygen will naturally lessen the pre-detonation points. That's why you'll see octane as low as 85 in Colorado, but at 1,000ft Phoenix the lowest is 87.

On modern vehicles there are knock sensors in the engine as well as low octane timing tables. If the engine detects knock it will switch it on to a lower timing table to prevent damage. This is how the fuel door label on performance cars went from "Premium Required" to "Premium Recommended". To get the full power out of a performance or higher compression engine, you'll need to use a higher octane rating so it doesn't knock and switch to the low octane timing table. Also, since higher octane fuel burns slower, that's where the better MPG comes from.

I'm not sure the specifics of the 6.4L engine and what compression and performance level it's built for, but if it's over 10.0:1 compression ratio and you want maximum power, consider the higher octane ratio. That said, people putting 91 in their Chevy Cavalier because they think its "premium" are wasting their money.
 
Owner's manual recommends 89 'for best performance'... I'll usually put that in when towing... otherwise I use 87 and make sure to hit TopTier fuel stations
 
Epsilon Plus said:
The octane number in fuel is simply a resistance to detonation. Marketing names like "mid grade" and "premium" are just that, marketing. It's not any cleaner or pure. The compression ratio and timing of an engine will dictate what octane it needs to resist knock (pre-detonation of fuel). Altitude and the lack of oxygen will naturally lessen the pre-detonation points. That's why you'll see octane as low as 85 in Colorado, but at 1,000ft Phoenix the lowest is 87.

On modern vehicles there are knock sensors in the engine as well as low octane timing tables. If the engine detects knock it will switch it on to a lower timing table to prevent damage. This is how the fuel door label on performance cars went from "Premium Required" to "Premium Recommended". To get the full power out of a performance or higher compression engine, you'll need to use a higher octane rating so it doesn't knock and switch to the low octane timing table. Also, since higher octane fuel burns slower, that's where the better MPG comes from.

I'm not sure the specifics of the 6.4L engine and what compression and performance level it's built for, but if it's over 10.0:1 compression ratio and you want maximum power, consider the higher octane ratio. That said, people putting 91 in their Chevy Cavalier because they think its "premium" are wasting their money.
Click to expand...
thank you, good info....Pete
 
Octane levels are not really an issue run 87 and you will be fine but when towing you can run 91 providing it has no ethanol you will see better millage. Ethanol is the mpg killer thats why you get terrible mpg with e85 if you have a (flex-fuel compatible vehicle)
 
I run 89, as I tow 50% of the time.
 
It's traditionally been 87 required, 89 recommended but in the the last 2020 manual I downloaded, they dropped the 89 recommendation and just said use 87.

octane.jpg
 
Your truck allows 85 o_O, I'm impressed. I would just stick with 87 personally. If it was my truck and I was under warranty, I would follow the manufactures guidelines
 
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