transmission ?

[Jackpine]

Originally Posted by Hunted1

I bought this one used with 5k on it. Has 20k on it now. Warranty just died and I figured I would extend it. The tow canned you need to run 87 octane though?
I've only used 85 in this since I bought it. Is it OK to use 85 octane with a tow tune or would you recommend 87?
I know stupid ? but the manual says 87 octane. The 87 is cheaper here by like 10 cents. I just don't want to mess anything up. I bet you have heard it all by now.

Thanks for all your answers. I figure that you never learn until you ask or read everything you can on the subject.

The octane question is a good one. Iowa is not a "high elevation" state I think, so I'm not too enthused about using 85 octane gas, even if it is cheaper. I've used it in Colorado (elevations 6,000+) without any noticeable problems though. The effect of higher altitude is to reduce the tendency of the air/fuel mixture to pre-ignite due to the reduced air density (which reduces absolute compression - the "relative" compression is unchanged, but since the outside air pressure is less, the compressed pressure inside a cylinder is also reduced proportionally).

I know the owner's manual says to use 87 octane - period, but I think high altitudes is one place you can discount that advice. I think though in Iowa, I'd stick with the manual, whether I was using a programmer or not. Every truck is different though. You may be fine with 85 if it works OK on the stock tune. With the Edge/Gryphon, you CAN reduce timing if you detect "pinging", which is the most common problem when running low octane fuel. If you hear pinging, set the timing back by -0.5 and see if it stops. You can adjust in 0.25 degree increments if further adjustment is needed.

- Jack