Octane numbers

what does everyone use in the 6.4 Hemi? 87,89 or 93? I personally use 93 with Lucas in every tank. Runs like a striped ape. Anyone use the same?

I run 85 up here. I will say, I saw a slight increase in throttle response when I ran a couple tanks of 91.

93 Sunoco, Yes, but I am told it’s a waste. Although audible and in audible knocks do retard the timing, so your correct I believe it runs better on 93 vs 87.

I run the mid grade of 87 octane up here at 6,000 feet in my Power Wagon due to it is gets driven down to a 4,600 feet elevation often. Above 6,000 feet elevation it probably would be fine with a lesser octane fuel like the 85 regular, but I stick with the mid grade.

If I anticipate in driving far out of state in some region below 4,000 feet in elevation, it gets an 89 octane fill up or a top off of an even higher octane fuel before I ever get below that elevation. The mid grade is 89 octane fuel below 4,000 feet. Got to go pretty dang far in any direction beyond Salt Lake City or Denver to ever get somewhat significantly below that altitude. Even Moab, Utah is at 4,000 feet in elevation and that's as low as it goes anywhere in a day's drive. The 87 octane fuel is fine to run there.

Mid-grade where I am is 89 and the truck handles great on that. If there is no mid-grade fuel I will put in 93, but I don't any difference between the two.

For those heading to Moab, Utah here's what's available in gasoline octane. 91 octane is the highest.


Also, nearby in Green River, Utah for the Ram diesel pickups the DEF is dispensed at the RV pumps.

I am running Shell 87 most of the time and don't feel any ill effect and I am in the GA. Manual says 89 or 87.

I thought with the new computer controlled vehicles, they should offer the higher octane at higher elevations. The MAS air flow sensor detects less air and pulls fuel out and adjust timing. Not like the old carb days when going over Vail Pass and sitting on the side of I 70 adjusting the carb trying to make it to the down hill side.

BevisIII said:

I thought with the new computer controlled vehicles, they should offer the higher octane at higher elevations. The MAS air flow sensor detects less air and pulls fuel out and adjust timing. Not like the old carb days when going over Vail Pass and sitting on the side of I 70 adjusting the carb trying to make it to the down hill side.

Click to expand...

https://www.quora.com/Why-New-Mexic...ou-destroy-your-car-engine-by-buying-this-gas

The first answer in the above link should address your thoughts.

The peak cylinder pressure is less at high altitude and so the speed of the combustion is slower. Less octane fuel is required for the slower combustion. The 6.4L is also producing less horsepower at higher altitude than it would at sea level.

I run 93. Now the truck is tuned and I continue to run 93. The 6.4 performed better IMO on the higher octane.

https://www.amsoil.com/newsstand/articles/high-octane-gas-boost-performance/

Higher octane fuel is to prevent engine knock.

My long ago 1968 Mercury with a Ford V8 required a minimum of 100 octane per the owner's manual.

Racing fuel is still sold today....

https://petroleumservicecompany.com/sunoco-standard-110-octane-race-fuel-54-gallon-drum/