Another newbie here....i just bought a 05 5.4l and it has a chip on it. im not sure exactly what model it is, it does say gryphon when u first turn it on? anyways my question is, the 2nd setting says 87oct. Well im a poor college student say i buy 85. Is there any chance this can harm my truck?


Thanks for the help.

Todd

 

You have a good chance of pre detonation. Timing and fuel octane work together to maximize power. if timing is to far advanced you could get pinging sounds which is very bad for your engine. If you run 91 octane you can use more advanced timing then with 87 octane. The same principles apply between 87 and 85 octane.

 

How is it that a "poor college student" can afford an 05 F150 but not a few cents a gallon more for higher octane fuel?

 

If you are in a high altitude area, you can run 85 octane on an 87 octane tune.

 

I've used 85 octane in Colorado with no problems that I know of. As glc said, if you're at high altitude, you're probably OK too. The higher altitude reduces the absolute compression in your engine, which means you can use a lower octane fuel.

- Jack

 

I worked my *** off all summer and had a decent trade in. Plus i got a way good deal on her. And my credit is way good to so i got a really low interest rate and have pretty good payments.
I just cant justify spending the extra coin on 87 oct...

Yeah i live in northen utah so were at right about a mile, so from the sounds of it i should be fine. but what if i was to reduce timing by .5, would that be worth it?

 

I would leave it alone unless you hear some pinging. You should be fine.

 

ok, cool. im guessing if this pinging starts, you would know it when u hear it?

 

Yes, it will sound like "marbles in a can". Normally happens at low RPM and high load (most often during acceleration).

- Jack

 

cool, thanks for all the help!