89 octane recommend, does it really make a difference?

[theblet]

I’ll run 87 until I tow

 

[Quint]

On my 2015 Bighorn and now my 2021 Bighorn, I run 87 octane around town and have never had a problem. When I tow I make sure to put in 89 octane.

How come everyone calls it "Top Tier" like we aren't allowed to say that FCA is recommending that we buy our gas at BP Stations? Is that taboo? I buy my gas at reputable stations no matter the marketing claim for their "detergents" in the gas.

 

[Joshua022]

I get a bit of knock randomly with 87, but not enough to worry me. I ran 89 and did not notice any difference other than $10 extra a tank.

 

[The Critic]

Most of the time you won't "notice" any knock/detonation unless you're datalogging with some sort of fuel management system in any car, but that doesn't mean it's ok and not having any detrimental effects. If you can actually hear/feel it happening that's probably bad.

This guy did some data logging and it clearly shows timing being pulled with 87.....more so than 89.

 

[CaptainCJ35]

This guy did some data logging and it clearly shows timing being pulled with 87.....more so than 89.

As would be expected. I would also expect it to happen dynamicly depending on load, atmospheric conditions, etc., where the ECU is consistently trying to get the best performance out of the engine as conditions and demands change.

 

[sppb32]

I use 87 I feel no difference from 89 or 93, when I had my 04 I did allot of engine work on it can headers, ported heads milled 0.020 that bumped the compression ratio a bit, I had to run 93 and use a tune for 87 to fight timing retard, but there is no knock, the ECU pulls the timing back to prevent it and it was only at part throttle, the truck was a beast with that setup, I see no reason to use high octane with a stock Hemi.

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[silver billet]

As would be expected. I would also expect it to happen dynamicly depending on load, atmospheric conditions, etc., where the ECU is consistently trying to get the best performance out of the engine as conditions and demands change.

It's worth noting that the ECU can only do so much. In my experience with the 87 while towing, it was pinging for 2 hours all the way home, especially up hills where I cringed all the way up. More than enough time for the ECU to notice something changed from premium gas to ditch water, but it still could not dial back the timing enough.

At a certain point we need to admit it; 87 is not enough.

 

[HSKR R/T]

I use 87 I feel no difference from 89 or 93, when I had my 04 I did allot of engine work on it can headers, ported heads milled 0.020 that bumped the compression ratio a bit, I had to run 93 and use a tune for 87 to fight timing retard, but there is no knock, the ECU pulls the timing back to prevent it and it was only at part throttle, the truck was a beast with that setup, I see no reason to use high octane with a stock Hemi.

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Sounds like whoever wrote your tune doesn't know how to tune if you had to run 93 with your 87 tune to prevent st and ltknk retard.

 

[HSKR R/T]

I get a bit of knock randomly with 87, but not enough to worry me. I ran 89 and did not notice any difference other than $10 extra a tank.

By the time you actually hear engine knock, damage is already being done to the engine, and you should definitely be worried.

 

[HSKR R/T]

On my 2015 Bighorn and now my 2021 Bighorn, I run 87 octane around town and have never had a problem. When I tow I make sure to put in 89 octane.

How come everyone calls it "Top Tier" like we aren't allowed to say that FCA is recommending that we buy our gas at BP Stations? Is that taboo? I buy my gas at reputable stations no matter the marketing claim for their "detergents" in the gas.

Because there is definitely a difference with "top tier" gas, and BP isn't the only one who is certified to label that way. It's more than just what detergents are used.

 

[RebelJC]

For those interested, I was able to get around 20.2 MPG mixed mostly highway 65mph max with some city. Second fillup 15.9 also mixed mostly highway but not caring about speed limit 65-85mph. Both with 89 octane.

 

[sppb32]

Sounds like whoever wrote your tune doesn't know how to tune if you had to run 93 with your 87 tune to prevent st and ltknk retard.

It was a caned tune from Superchips, not custom tune, it wasn't available at the time for the 04.

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[sppb32]

Even at 125 mph I didn't hear any knock

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[James1414d]

I live in Oregon where we can't fuel are own vehicles. I noticed yesterday the genius who filled me up used 87 when I asked for 89. Guess I'll find out if there is any difference.

 

[GadgetMason]

I'll go with the manual...

 

[theblet]

I'll go with the manual...

So use which ever one you want ?

 

[HSKR R/T]

So use which ever one you want ?

Do spends if you use what is recommended, or what will degrade performance, but still work

 

[theblet]

I have no trouble with 87 not towing. Don’t need the extra power. Might try 89 one day just to see how much mpg goes up but it probably won’t be enough mpg gains to make it worth it.

 

[HSKR R/T]

I have no trouble with 87 not towing. Don’t need the extra power. Might try 89 one day just to see how much mpg goes up but it probably won’t be enough mpg gains to make it worth it.

Just remember, it takes more than one tank to adaptives to change and make a difference.

 

[Timeless]

Just remember, it takes more than one tank to adaptives to change and make a difference.

Are we sure about this? Seems the sensors would be monitoring this in real time.