waltonksm

I have a completely stock 1993 F-150 XLT with a 5.8L V8, 4 x 4. Most places the "books" call for an Autolite 24 plug (temp range 4). Will I see any difference if I go to an Autolite 25 (temp range 5)? By difference, I am looking at mileage, plug life, etc. I live in Alaska if ambient temp makes a difference in which plug to use. Original engine, with 185K. I have an even more ancient (from the 70's), very small camper in the box, so it has extra weight on it. I am not sure if any of this would make a difference for the recommendation. Thanks

Marc D

All cars have plugs that are factory specified based on motor specs. The move to a hotter plug could possibly cause pre-ignition (knocking) depending of your driving conditions and weather. Normally the radiator thermostat will keep the engine operating temp in correct range 180 to 190 degrees so changing heat ranges on the plugs is not recommended. The only condition that would allow the use of the higher heat range is if you have a cylinder that is using oil, either by the rings or a valve guide.

waltonksm

Thanks for responding. I was told that I have one "weak" cylinder: No. 8, with lower compression. So it might make sense to use the 25 in this hole only?

Marc D

Yes. You can use the hotter plug in one hole. I would even go as far as checking the plug after a few thousand miles to be sure it's not super white, indicating too lean a burn. If it is go back to the stock plug.