85 Octane

[Mike Main]

My '10 Trac with the 4.0 engine calls for 87 octane. In Colorado they sell 85 octane everywhere and it is significantly cheaper. My F-150 302, Town Car with 4.6 and Freestyle with 3.0 all run fine on 85 octane even though the manuals all call for 87.



I have not looked at the 4.0 compression ratio compared to my other vehicles to see if there is more reason for an 87 requirement. Is anyone else running 85 octane in a 4.0?

 

[H D]

At Colorado's altitude, 85 is just fine. Its as good as 87 at the lower altitudes. If you leave the higher elevations, fill up with higher octane beforehand. I'm sure someone will give chime in shortly with the technical details.

 

[John G]

High altitude means low pressure in the air. Compress that thinner air, and it doesn't generate as much heat, so it's less likely to detonate.



Drive down to low altitude and high temperatures with that fuel in your tank and you might have a problem.

 

[Bill Koonce]

Good point about the altitude.



Does the 4.0 have a knock sensor? In theory the knock sensor should protect the motor at lower altitudes. Keeping a bottle of octane booster on board wouldn't be a bad idea, just in case.

 

[George T]

Woooooo

An active Colorado member:banana::grin:

Im up in Thornton, maybe ill see you on the streets sometime.