Octane

[retired]

These engines are built at the same spec; if my truck pings on 87, so does yours. It's really that simple.

If you say "my truck doesn't ping", I promise if you wire up an obd2 data logger and look at the results, you will see it there in black and white.

Your truck most certainly pings on 87, doesn't matter what quality of gas you use. It's the low octane that is the problem.

your 5.7 (that is what you have in profile info) and a 6.4 are the same specs? I guess I will take my chances. I have burned enough of both and mine runs just fine on either so why pay more for the same.

 

[ramffml]

Point taken, I won't go so far as to say that the 5.7 and 6.4 will react 100% the same way with 87. However, if you can find a bunch of guys saying "I hear pinging in my 6.4 with 87" then it will be happening in yours too.

Sometimes it's not enough for us to rely on our ears/senses. A computer/logger would be able to show how badly these engines ping on 87, and even 89 isn't all that good. Engine pinging is not a good thing to have happening, so the more we can reduce it and/or the chance of it, the better it is.

A lot of us spend thousands on mods or toys etc, I always feel a little baffled when I see them arguing against a higher octane, logically it doesn't make sense to me to run the cheaper stuff but I guess we're all different with different spending priorities.

 

[HEMIMANN]

How do I give 20 likes to a gasoline thread where a guy knows WTF he's saying??

Meh - n.p. There's a bunch of us engineers, techs, and hobbyists on here. That's the point, right? I've learned as much or more as I've assisted.

Those of you who've never heard, ahem, "pre-ignition".....trust me you'd know it. We used to have fun developing new gaseous-fueled commercial engines. The spark ignition timing map was always hazardous with propane fuel, as propane's octane level is very low. There ain't much room between 1st ping and *KABOOM*! Blew more than one motor in development.

 

[Riccochet]

i have ran 87 for about 20,000 miles and havent noticed jack. i ran 89 from about 1000-1500 miles and noticed 0 difference in all aspects.

You won't notice it. It won't be pinging because the ECU pulls timing.

 

[2012RAM1500RT]

Earlier this year I took my truck to the track. I had planned on putting 93 octane in it but didn't get a chance to drive it enough to run the 87 octane I had in it out. I ran the 1/4 mile all day in the 14.2 times. Ran a best of 14.1 and never "heard" the first ping. That's with a stock engine with only a tuner from Hemifever on the 87 tune he gave me. 135,000 miles on it also. Would have loved to see what it would have done with 93 octane and the 93 tune i have also. I really wouldn't expect it to be a huge difference. I was pretty happy with those times beings I'm driving a 5000 lb. brick. If I'd have "heard" I little ping I would have added a gallon or 2 of racing fuel to it. Point being I know that higher octane is better but it's not like back in the day when the difference was a lot more noticeable. There's no argument from me there.

 

[Bramic71]

Hello,
Sold my '18 2500 6.4 and bought a new 2021 2500 6.4 with a 3.73 4x4 and have a question regarding octane. I know my 18 owners manual said mid grade 89 was preferred however the 21 owners manual says nothing about mid grade 89 and states to use 87 (without ethanol). So I'm looking for input from the board regarding 87. Also will the 3.73 get better MPG than the 4.10 I had? Thanks for the info.

David
Michigan's thumb

I know the 5.7 is a different animal than the 6.4. I have had absolutely no knocking running 87 at lower altitudes. We just finished up a trip through the high desert and mountains of Utah and Colorado up to over 14,000ft. In the higher elevations 87 was migrate, and I even ran 85 with zero issues. No knocking what so ever. I believe elevation also plays a part in what will work. Have a great day gentleman and ladies.

 

[Schectadon]

This is in my 21 Laramie 1500 manual. That said, I buy from Costco so it is either 87 or 91. At Costco the 91 cost the same as 89 at Other gas stations. So I usually buy 91.

 

[HEMIMANN]

That's because Costco 91 octane is higher than 10% ethanol. Ethanol is an octane booster, but has less energy density than gasoline - and more solvency that harms plastic parts. And - your engine is not designed to benefit from 91 octane......your spark ignition timing does not advance for 91 octane. Stop buying it.

This said, Costco is a Top Tier registered gasoline, so that is good. Top Tier gasolines have more than the minimum required detergent additives, and have been test-proven to provide far superior engine cleanliness on intake valve stems and fuel injector nozzles.

 

[Dean2]

That's because Costco 91 octane is higher than 10% ethanol. Ethanol is an octane booster, but has less energy density than gasoline - and more solvency that harms plastic parts. And - your engine is not designed to benefit from 91 octane......your spark ignition timing does not advance for 91 octane. Stop buying it.

This said, Costco is a Top Tier registered gasoline, so that is good. Top Tier gasolines have more than the minimum required detergent additives, and have been test-proven to provide far superior engine cleanliness on intake valve stems and fuel injector nozzles.

At least here in Alberta, Costco Premium has ZERO ethanol in it. It and Shell are the two premium fuels we all use for small engines, boats etc because of it. It is rated Top-Tier here too. Their Premium is usually less expensive than most other places for 87 Octane.

 

[Elkman]

Octane is ONLY a measure of the pre-ignition point for gasoline. The higher the compression ratio of the engine or older the engine in terms of carbon buildup inside, the more prone it will be to pre-ignition of the gasoline. With computer controlled ignition if the fuel has too low an octane value then the computer will retard the spark to minimize pre-ignition and prevent damage to the engine.

If an engine is specified to use "87 to 89" octane gas then the lower octane rated fuel is what should be put in the gas tank. One caveat is that the fuel economy "may" be higher with the 89 octane gas. I had a coupe with an engine that required 93 octane gas for optimum performance. I could put 89 octane gas in the tank and the only result was a loss of 5-10 hp and about 10% fewer miles per gallon as the retarded spark resulted in poorer fuel economy. With my car the cost per mile driven was roughly the same with 89 or 93 octane gas in the tank.

If I was using a pickup to tow a very heavy trailer then going with the 89 octane for the 5.7L engine "may" provide slightly more horsepower and torque.

 

[HEMIMANN]

Octane is ONLY a measure of the pre-ignition point for gasoline. The higher the compression ratio of the engine or older the engine in terms of carbon buildup inside, the more prone it will be to pre-ignition of the gasoline. With computer controlled ignition if the fuel has too low an octane value then the computer will retard the spark to minimize pre-ignition and prevent damage to the engine.

If an engine is specified to use "87 to 89" octane gas then the lower octane rated fuel is what should be put in the gas tank. One caveat is that the fuel economy "may" be higher with the 89 octane gas. I had a coupe with an engine that required 93 octane gas for optimum performance. I could put 89 octane gas in the tank and the only result was a loss of 5-10 hp and about 10% fewer miles per gallon as the retarded spark resulted in poorer fuel economy. With my car the cost per mile driven was roughly the same with 89 or 93 octane gas in the tank.

If I was using a pickup to tow a very heavy trailer then going with the 89 octane for the 5.7L engine "may" provide slightly more horsepower and torque.

It is the entire point of higher octane gasoline to permit advancing the spark ignition timing to get more power and use less fuel. Hence the 100 octane aviation gasoline of world war II.

 

[ramffml]

If an engine is specified to use "87 to 89" octane gas then the lower octane rated fuel is what should be put in the gas tank.

"lower"? "should"?

You SHOULD be putting in 89. You put in 87 when you don't care about your truck and just want to get from A to B.

 

[392DevilDog]

I started using E15 88 octane 7 tanks ago. So far many road trips and hauling and just completed my 2nd tow with it.

This is what I will be using going forward.

It is exactly what it says it is right in between. I have found it is better than 87 and about the same as 89.

And at 20 cents cheaper than 87 and 50 cents cheaper than 89...it is saving me about 13 bucks a fill up.

I like saving money and getting the same performance.

And it is better for the environment...or farmers...I forget

 

[PCT]

You won't notice it. It won't be pinging because the ECU pulls timing.

100%, but what i am saying, i haven't noticed any difference in power, or MPG when using either/or. So i decided to stay with 87... Unless someone can provide #'s on HP and show how much i am actually loosing using 87, prob gunna stay. I feel safe running it. Here in california difference betweeen 87-89 can be upwards of 30 cents a gallon...
My local Arco:
3.99 for 87
4.39 for 89
4.89 for 91

 

[retired]

my guess is if you put them on a dyno it would be very small and on a 7000lb rig ie a 2500 with 6.4 it would be dead even in a drag race especially if at 3000 feet elevation or above...I don't drag race or drive in a manner ie lugging and then punch it etc that would cause ping to be an issue. If I were pulling at max weight I would run 89 or 91 but just daily driving not going to.

 

[RedneckHippy]

2019 gasser manual - do with it what you will

 

[392DevilDog]

View attachment 4727582019 gasser manual - do with it what you will

That is what i did. 87 to 89...so I picked 88 and under 15% ethanol...all rules followed

 

[johnwayne]

Well if it says 89 octane run 89. I cant imagine 87 doing any harm. HOWEVER being under warranty .... I have seen them void warranty for less. Due what it says. No brainer to me

 

[Mrbyh20]

I’m surprised anyone is finding a truck to buy. I’ve been looking for a ‘22 but they aren’t out yet I guess and there’s a very limited supply of ‘21’s remaining here in Phx that I’ve seen. Dam computer chips. Back to the fuel grade, I run 87 once then next tank 89 kinda back and forth. It’s cheaper to run the 87 then buy a can of high octane fuel supplement from inside the store and add to the tank. However this is just my opinion. No issues with how the truck is running with regarding truck running wise. No difference in mpg.

Bit of an odd question for the masses. Why does all the gas stations still say 3 different grades of unleaded has since we no longer have the regular grade gas as an option. Lol. Just curious on what others think.

enjoy the new wheels.

 

[denali2ram2500]

I've recently switched from using 93 all the time for the last 4 months to 87 (So far two full tanks) and didn't notice any change in performance or fuel consumption.

2021 Ram 2500 CC 4x4 Tradesman 6.4L Hemi