Hemi 6.4, gasoline. 87 or 89.

[Ribtipram]

high octane does i repeat does not create more power. Its actually harder to burn. In a high compression environment low octane burns to fast and you have spark left and thats what causes detonation(spark knock ping) high octane being harder to ignite stays in the chamber longer. Thats why supercharged turbo and naturally aspirated high compression engines need high octane. An engine with a compression ratio in the 9's will be fine at 87oct in the 10's89oct you get into high 10's+ its time for 91/93. I will admit my truck is faster when clean,new oil,plugs ex ex

 

[HammerHead]

You know I've ran 87 for over a year straight in mine and coincidentally today I filled up with 89. I swore to myself the midrange felt noticeably healthier on the way home.

I agree, the 6.4 runs better with 89.

 

[dhay13]

Yep. Higher octane does not create more power. What it does is allow the engine to operate to it's potential. If an engine senses detonation or pre-ignition the spark retarder will retard the timing which will reduce power. Running the proper octane fuel will prevent these conditions and allow the engine to run at it's peak. Running higher octane than is needed is a waste. As long as the engine is not experiencing detonation/pre-ignition then you don't need any higher octane than that. Higher octane fuel is more resistant to ignition.

 

[SouthTexan]

high octane does i repeat does not create more power. Its actually harder to burn. In a high compression environment low octane burns to fast and you have spark left and thats what causes detonation(spark knock ping) high octane being harder to ignite stays in the chamber longer. Thats why supercharged turbo and naturally aspirated high compression engines need high octane. An engine with a compression ratio in the 9's will be fine at 87oct in the 10's89oct you get into high 10's+ its time for 91/93. I will admit my truck is faster when clean,new oil,plugs ex ex

Yes, modern compter controlled engines that are variable valve and can adjust timing can make power with higher octane fuel. If the knock sensor does not detect knock, it will advance timing creating more power until knock is detected.


Here is a good article of a few engines being tested. There is another I can post from AAA showing more data, but I am on my phone and will have to wait until I can find it on my computer.

Is Premium Gas Worth It? We Test High Octane on 4 Popular Vehicles

 

[tjfdesmo]

There will be a run on VP 110 race gas tomorrow

 

[G. Mcpherson]

There will be a run on VP 110 race gas tomorrow

You have a New Ram!

 

[tjfdesmo]

You have a New Ram!

Yessir, it is gooooooood to be back in a Cummins!

 

[G. Mcpherson]

Stock Photo? I agree!

 

[RoadRamblerNJ]

We all know 93/91 is harder to burn then 87 or 89 right. Its a Compression thing. Run the lowest you can unless she spark knocks. Then bump it up one grade. Most likely the 6.4 will never ping off 87 unless its crazy hot out and pulling a heavy load(maybe). Mtofell is right the Absence of ethanol will always bring a couple of mpgs more.anything more then 89 for are 6.4's is a Waste of money.

Yes Sir, well stated.
By federal law, any and all vehicles sold in the USA must be able to run on 87 octane gasoline without any damage occuring.

You might see improved performance with a higher octane gas but, you will not do any harm by running 87.

That's why 89 is just "recomended", not "mandated".

Personally, with my 09 4WD 1500 5.7 and my '17 4WD CCLB 6.4 I've never noticed any difference in performance between 87, 89 or 91/93.

Sorry about all the arguing to the contrary Dad. You were right. I was wasting my money.

 

[Rwgarrison23]

Does the hot weather contribute to how it drives between two different grade gas?

 

[RoadRamblerNJ]

My opinion, 30 yrs ago, really hot weather could be a factor with an engine pinging.
Our newer stuff is fuel injected and controlled so accurately by a computer, it can react to changes in temp and make adjustments on the fly. It's kind of a thing we don't have to worry about any more.

Edit: Above experience is all below 1000 ft elevation. Higher altitudes may be different.

 

[Rwgarrison23]

I think I live above 3400 feet sea level.

 

[RoadRamblerNJ]

I think I live above 3400 feet sea level.

That's about the elevation my old Harley Shovelhead quit running right when going up Mt. Washington long time ago. Quit running all together at about 5000 ft. Two of us had to mess with the carbs. Never did get anywhere near the top, LOL. Oh well, all the cold beer was at the bottom anyway!.

 

[SouthTexan]

Does the hot weather contribute to how it drives between two different grade gas?

Yes. Very much so.

 

[SouthTexan]

Yes Sir, well stated.
By federal law, any and all vehicles sold in the USA must be able to run on 87 octane gasoline without any damage occuring.

You might see improved performance with a higher octane gas but, you will not do any harm by running 87.

That's why 89 is just "recomended", not "mandated".

Personally, with my 09 4WD 1500 5.7 and my '17 4WD CCLB 6.4 I've never noticed any difference in performance between 87, 89 or 91/93.

Sorry about all the arguing to the contrary Dad. You were right. I was wasting my money.

I never heard of such a law. I know I have had vehicles that you could only run premium

 

[tidefan1967]

I never heard of such a law. I know I have had vehicles that you could only run premium

GM's 6.2 V8 says 91 octane minimum in the manual and I have yet to see a luxury car that called for anything less than 91. Of course all Ford engines say 87 octane minimum and the newer 3.3 and 5.0 have 12:1 compression.(direct injection) Any vehicle should run on 87 but not necessarily run well.

 

[RoadRamblerNJ]

I never heard of such a law. I know I have had vehicles that you could only run premium

I will contact the State Trooper that explained that to me and try to find the statute.

 

[1500ram12]

I will contact the State Trooper that explained that to me and try to find the statute.

The only thing I can find is federal law about minimum Octane being produced/ manufactured. Nothing on a law that state's all vehicles produced have to be able to run on 87 Octane. A manufacturer of a vehicle can say it's recommended that it's vehicles only be run on whatever Octane they want, it's probably a loop hole for engine warranty and performance claims


2018 2500 6.4L Tradesman

 

[RoadRamblerNJ]

GM's 6.2 V8 says 91 octane minimum in the manual and I have yet to see a luxury car that called for anything less than 91. Of course all Ford engines say 87 octane minimum and the newer 3.3 and 5.0 have 12:1 compression.(direct injection) Any vehicle should run on 87 but not necessarily run well.

Yes. Your last sentence. Everything has to be able to run on 87 without causing damage.
I've also had vehicles that quote a higher octane as the "recomended fuel".
I've also built engines with higher compression than anything sold commercially but, that's not what I'm referring to. My street motors got fed nothing but Sunoco 260 leaded fuel. When we went to Englishtown to race, it was 50% Sunoco 260 leaded and 50% a purple aviation fuel octane.

"88 Octane, also known as E15, consists of 15% ethanol and 85% gasoline. 88 Octane is approved for use in all model year 2001 and newer vehicles by the U.S. Environmental Protection Agency – that's nearly 9 out of 10 cars on the road today.
https://www.mnfuels.com › 88-octane
88 Octane - MNFuels"

 

[RoadRamblerNJ]

Still looking. Also will contact the Trooper that told me about this.