87 or 89 or mix

[B0RN2W1N]

I hear that the Rebel can run on both 87 or 89. What are the benefits other than RAM recommending it but still stating it's fine to run 87 octane? I assume it's not the best to mix so would you have to wait to get to E to fill with a different fuel? 89 is really just a mix of premium and regular gas.?

 

[vincentw56]

Running 87 is fine as long as there is no knocking. You won't get the full performance of the engine. If you are towing, I won't go under 89. I run 87 on long trips to save a few dollars. But mostly run 89. Premium is not a mix of 89 and other gas. It's got a higher octane which is what those numbers mean. It's usually the same gas with just octane added. Sometimes they add additional additives like detergents and stuff.

 

[B0RN2W1N]

Running 87 is fine as long as there is no knocking. You won't get the full performance of the engine. If you are towing, I won't go under 89. I run 87 on long trips to save a few dollars. But mostly run 89. Premium is not a mix of 89 and other gas. It's got a higher octane which is what those numbers mean. It's usually the same gas with just octane added. Sometimes they add additional additives like detergents and stuff.

Thanks for the info, this was info I was given from dealership lol. What is this "knocking" you can hear? I'm usually a city driver with 30 miles driven in the highway to work.

 

[Richard320]

Thanks for the info, this was info I was given from dealership lol. What is this "knocking" you can hear? I'm usually a city driver with 30 miles driven in the highway to work.

You've never heard "pinging"?

Generally when under a load, like accelerating from a stop, you'll hear a rattle like a noisy lifter that should fade away as you get up to cruising speed and lighten up on the pedal. That's pinging. You might also hear it going up hills. The truck will respond by retarding timing to stop the pinging, which will increase fuel consumption and decrease performance. If the mileage doesn't take a hit and you don't hear pinging, use the 87. But if you do note reduced performance or worse economy, gp back to 89.

 

[B0RN2W1N]

You've never heard "pinging"?

Generally when under a load, like accelerating from a stop, you'll hear a rattle like a noisy lifter that should fade away as you get up to cruising speed and lighten up on the pedal. That's pinging. You might also hear it going up hills. The truck will respond by retarding timing to stop the pinging, which will increase fuel consumption and decrease performance. If the mileage doesn't take a hit and you don't hear pinging, use the 87. But if you do note reduced performance or worse economy, gp back to 89.

No, I'm coming from a 2.7 Turbo Silverado which I always put 87 and I never heard any knocking or pinging before. Just the good ol jumpy RPM's because of the poopy 8 spd trans

 

[silver billet]

I run 89 and will never run 87 again. My truck runs better with 89 and I don't see the point in spending $50,000 on a truck only to try and save $10/month on fuel.

 

[theblet]

87 unless towing

 

[B0RN2W1N]

I run 89 and will never run 87 again. My truck runs better with 89 and I don't see the point in spending $50,000 on a truck only to try and save $10/month on fuel.

Yeah that's what I also thought. Here in the PNW 89 is about 15-25 cents more expensive.

 

[SD Rebel]

Some manufacturers do this different, but generally everything is designed to be run on 87 in some form or other, while there could be a higher octane recommendation for best performance and/or fuel economy.

RAM chooses to state 89 is recommended for the best performance, while also stating 87 is acceptable. Ford on the other hand words it different, they state 87 is the recommended octane, but if you want some extra performance for towing for example, they recommend 91.

Either way, it essentially means the same thing.

 

[silver billet]

Also what clinches the deal for me; the truck defaults to the 89 tune. When it senses knock, it retards timing. So the knock (which is a bad thing physically) is there first, then it "saves itself" by detuning. I'd prefer to have the truck run without knocking in the first place.

 

[SD Rebel]

Also what clinches the deal for me; the truck defaults to the 89 tune. When it senses knock, it retards timing. So the knock (which is a bad thing physically) is there first, then it "saves itself" by detuning. I'd prefer to have the truck run without knocking in the first place.

Good point about "base tune" of these motors. The HP rating of the RAM 5.7L is based on that 89 octane, whereas in my Ford example, it's based on it's 87 octane rating.

I personally use Costco 91 octane, because it's Top Tier classified fuel that meets the Mopar recommendation while also being cheaper than most other fuel stations 87 octane.

 

[Bpebler]

I run minimum 89 in all vehicles. The modded Trans Am I had before I sold it and the truck always gets 91 or 93. A little bit of that choice also has to do with the fact that work pays for vast majority of fuel and although I’m not towing, I’m driving long hours with a lot of hills and a decent amount of cargo.

 

[Dewey]

I’m on my third Hemi since 2013 and have only run 87. No issues and never heard any pinging even when towing my boat. Figure I saved over $5000 during that time not running 89. Not everybody needs it.

 

[silver billet]

Good point about "base tune" of these motors. The HP rating of the RAM 5.7L is based on that 89 octane, whereas in my Ford example, it's based on it's 87 octane rating.

I personally use Costco 91 octane, because it's Top Tier classified fuel that meets the Mopar recommendation while also being cheaper than most other fuel stations 87 octane.

I have run 91 octane before too, but somebody on a different forum made the claim that higher than needed octane has 0 benefit and may actually lead to carbon deposits due to incomplete burns. So now I just run 89 lol.

 

[silver billet]

I’m on my third Hemi since 2013 and have only run 87. No issues and never heard any pinging even when towing my boat. Figure I saved over $5000 during that time not running 89. Not everybody needs it.

You're welcome to run what you want, but "I don't hear pinging" is not evidence that there is no pinging. Objectively speaking we know these trucks ping on 87, that is a fact. They're designed to run this way (tuned for 89, but retard timing when it hears knock on 87).

 

[Dewey]

You're welcome to run what you want, but "I don't hear pinging" is not evidence that there is no pinging. Objectively speaking we know these trucks ping on 87, that is a fact. They're designed to run this way (tuned for 89, but retard timing when it hears knock on 87).

If I was towing over 5000 lbs obviously I would use 89. Over 250,000 miles running only 87 octane is pretty good proof for me and perfectly suited to my driving requirements.

 

[Darksteel165]

My truck gets way better mpg with 89\93 (no 91 here).
You can run logs with a tuner to check if you are pinging. MIGHT be able to do it with Torque also, not 100% sure.

 

[silver billet]

Over 250,000 miles running only 87 octane is pretty good proof for me and perfectly suited to my driving requirements.

That's certainly good to hear. I try to run the best oil and filters I can find too. No guarantees that it helps or makes a difference but I just feel better knowing my truck has every chance at ekeing out the longest life (within reason). Again considering the price I paid for it.

 

[SD Rebel]

I have run 91 octane before too, but somebody on a different forum made the claim that higher than needed octane has 0 benefit and may actually lead to carbon deposits due to incomplete burns. So now I just run 89 lol.

I would run 89 octane too, but it's either 87 or 91 at Costco. Though I've heard about the excess carbon built up on older engines with more stringent set of tuning parameters.

However, modern engines are always adjusting the timing up and down depending on the fuel available, I've seen dyno test that show slight improvements on 3rd gen Hemis the higher the octane, all the way up to 93. If I use 91, I don't think our engines are locked into a 89 tune, but it's more flexible.

But could be wrong, would love to see something that was definite on that. I guess I can mix 91 & 87 to get 89, but swiping twice at Costco gas could mean me getting purged by the drivers behind me

 

[Mr.Grid]

If I was city and limited 75+ mph driving I’d try using 87. I’m always on the highway when not towing a 7k# trailer over 60% of the time. I use 93 for towing and it is very noticeable compared to 89 when climbing grades of 3+%. For me, 93 displays better fuel mileage when towing and I’m filling up with less fuel between my normal planned tow stops. I also do Not use Tow/Haul. Not needed.