Premium Gas

[Bubba2016]

Looking at new 2500 with 6.4 gas. I see they recommend premium gas. Has this always been true and does anybody run regular instead? Thanks

 

[rule18]

Premium has been suggested for Hemis for as long as I can remember. That said, a lot of people (me included on my last two Hemis) run 91 which seems fine. I'm sure others will chime in.

 

[Gamedog]

Yup, I run mid grade in my PW and did the same on my 1500. Never an issue.

FYI mid grade here in Colorado is 87...

 

[MSgtZ]

So I have a 2014 with the 6.4L. My owners manual recommends regular unleaded (87) for it. (I have had mine for a month now and have been using regular with no problems in this Texas heat.)

 

[Troutman561]

I have a 1500 and I believe 89+ is recommended. I have used 87 and 91 and noticed 0 difference.

 

[Travelin Ram]

The requirement is 89 -which is mid grade- for maximum performance or words to that effect.

Runs just fine on 87; perhaps you’ll get 10 hp less or some minimal loss of performance due to the PCM scaling back timing. No harm will be done.

 

[NDanecker]

Before my engine build I ran multiple tanks of 87, 89 and 91/93. It ran much better with 91/93 but took 2 or 3 tanks to notice the difference. I believe it takes a few tanks to get a true 93 octane rating and the ECM may learn new mapping, but not 100% sure on that part. If it see's knock it adjust immediately. Either way - runs much better off idle and part throttle acceleration with 93.

Is it worth it? Up to you.

If you tow heavy, high air temps and at/near sea level go with higher octane.

If you don't tow, colder air temps and high elevations you can go with lower octane ratings.

 

[Ram 1970]

Ran 87/91/94 and 94 w/octane booster during my 2000-mile vacation trip recently. No performance difference at all between the octane levels. No MPG difference. I now run 87 all the time.

 

[Elkman]

The 93 octane is to prevent pre-ignition or knocking with the high compression engine. When you put in a lower octane rated gas the engine computer will retard the spark to compensate. No knocking but poorer fuel economy with the lower octane fuel.

It is also not a hard indicator as mixing 5 gallons of 87 octane gas with 5 gallons of 93 octane does not result in a mix at 90 octane but closer to 92 octane in its performance.

For heavy towing I would pay for the 93 octane gas and burn it in the engine. For around town trips it really does not matter.

 

[bm02tj]

I only run 87
Only use high volume stations so no old gas

 

[NDanecker]

87 through 94 octane (or whatever) has the same energy density so using one over the other does not make your truck more powerful. However, a higher octane rating will decrease the ability of igniting prematurely creating piston vibration or knock (which is bad). Your engine has knock sensors that look for knock and will pull timing to help prevent this knock which will prevent your motor from making full power. Knock can happen at all rpms but frequently happens when lugging the motor (lots of fuel in lower gear or rpms). So - if you feel that it runs better (which I did with higher octane) its because it wasn't pulling timing when around town under part throttle accelerations and using lower gears (not downshifting).

Quality of fuel and ethanol play a larger part in energy density. Good fuel and lower or no ethanol is best.

Diesel fuel has I think 10 or 20% more energy than gasoline per volume which is one of the reasons they get better mileage (or can if the EPA would keep their hands out of the emission crap).

 

[ramffml]

Actually in my experience knock is far more noticable when working it. Going up a steep hill and revving it out, pulling a trailer, anything where it's going past 2500 - 3000 rpms and sure as the sun rising, knock is going to happen.

Most people just don't hear it because they don't recognise it. I grew up pushing an 80 caprice and that thing knocked so bad on regular gas going up hills even a child could pick up the noise. Once you hear that sound, it's unforgetable. And my hemi knocks on 87. Not badly, but it's there.

 

[jasonw]

87 should work fine, I just would try and do a tank or two of 89/91 before towing or loading it up.

Not tested it with the 2020 yet, and I don't plan to, but on my 2014, only time it'd knock on 87 is if the 87 contained ethanol and I had to use WOT. Only did that once, and that was because I had no choice at that location.

The tuner I had on it was running an 89/90 octane tune, and it actually liked 87 octane with no ethanol better than 91 octane with 10%.

Unfortunately, most stations out here put ethanol into everything. Was a touch sad that Costco, when they built their new store out here, put in a station with only ethanol pumps. Other Costco pumps I've visited across the country have ethanol and non-ethanol choices usually.
So I use the 91 octane, which offsets the 10% ethanol a bit. Its not a direct relationship between the two, but it did help eliminate knocking.

When travelling, I try to use ethanol free pumps. Helps a bit with MPG too, my 2014 would see around 1 MPG in town, 2 MPG highway boosts when ethanol wasn't used. And that was consistent, otherwise I would have wrote it off to other random factors.

 

[dtru1222]

I have owned 4 2009+ 5.7 Hemi's now, 3 trucks and 1 Challenger. Every single one of them had ST and LT knock on 93 gas in Texas. This isnt the old days, you dont always hear knock in these newer engines. The sensors can pick up what you are not hearing and reduce timing. The only way to be certain is to datalog your ST/LT knock retard. Unless you have the actual data, you are just guessing.

It seems to be very region specific but 75%+ of the people who datalog and report back are seeing timing reduction due to knock on 93 octane, this coming from both Challenger and Ram forums. Just to be clear, this will not "hurt" your engine and you may run 87 and everything seems "fine". Thats the point of the timing reduction, to prevent damage. The testing I have done shows that the increased MPG I get outweighs the increased cost at the pump.

 

[yakalong]

87 has worked fine for me with no complaints. Towing or not the hemi has worked just fine, I'm not spending extra for something that is not needed, just my opinion

 

[Trailmaker]

Looking at new 2500 with 6.4 gas. I see they recommend premium gas. Has this always been true and does anybody run regular instead? Thanks

The 6.4 ask for mid grade though you can run the 85 or 87 octane depending on elevation the 89 (in Texas) keeps the msds from rattling when active. The truck going into 4 banger mode seems to handle eco mode without the rumbling effect most guys complain about. The speed of timing on the 6.4 prefers the mid grade if available.

 

[wgreggking]

I run 87 or 89. 89 seems "quieter" especially when towing. Around town, 87 OK running empty. I always use top tier if possible, Chevron Costco Shell 76 Mobil. Had a few times thought I had bad gas from old dilapidated gas stations. Try never to run below 1/4 tank.

 

[turkeybird56]

89 Octane recommended octane for the 5.7L Hemi. 87 acceptable... Yer wallet, decide, LOL.....

FWIW: I always run 89. I only use 87 when topping off a LIL, or I am in a place where I just have to have fuel and they only have 87 available. I have run 89 on every Hemi I have owned. Used to run Amoco 93 or High End Sunoco in my earlier Chevy's, late 60's, but that is an entirely different discussion.

 

[WmHBonney]

Howdy. I run 90 non ethanol instead of the 89 or 87 with 10% ethanol. If I remember correctly, there is more energy available in a gallon of non ethanol gas than there is in a gallon of the 10%. My truck only has 300 miles on it, but I have used the same gas in other vehicles and have seen increased mpg.

 

[Sandevino]

I’ve run both 87 and 89 octane in mine and really only tell a difference never. I had fuel points I had to use and 89 mid grade cost $1.09 so I went with that...lol