Hi,

I have a new 05 Expedition and work pays for my gas. Will it help or hurt if I run higher Octane gas? Also, I was told years back put only one brand of fuel in a vehicle, Is this just a myth?

 

Use the lowest octane you can without pinging. There isn't anything to gain by burning a higher octane fuel unless compression or timing requires it.

 

the expy will perform best on 87. why would you want the fuel to burn slow in a engine that does not need it to?

 

please explai? My question was is a higher octain better than a lower octane in the Expedition. Please explain your answer.

 

Higher octane fuel has a higher autoignition temperature than a lower octane fuel. The expedition was tuned using 87 octane, so the timing curves are all set to be optimal for that octane fuel. The mixture ignite later in the cycle than was intended reducing performance and efficiency. If timing is advanced to fix this, it might run a little better due to the more advanced timing, but the fuel itself won't work any miracles.

 

Thanks for the education. Makes sense to me now. So, unless I reprogram the trucks computer to compensate for the higher octane, don't bother. Thanks.

 

Yeah, I wouldn't do it, even if someone else was paying for my fuel. A tank of premium won't hurt anything from time to time, but it's not necessary.