Navi Newbie here, ..........again.

I don't have my Navi owner's manual right in front of me, but I think I read in there that Ford specs 91 octane for the 32 valve engine. I've only run about three tanks of fuel through it, but out of habit I put 87 octane in it each time. And what little I've driven it, it seems to run just fine. For now, I'll probably just keep using it, but may up the octane in the heat of summer and/or when towing.

Any problems with running the 87 octane fuel in the Intech?

And I've been surfing the net looking for info on this E10 (10% ethanol) fuel. It seems like some countries require an E5 blend that has around 95 octane. And I believe here in NY State most fuels are E10 in the winter season since MTBE is banned. Does this mean that if I grab the '87 Octane' nozzle, it should have adequate octane for the Intech?

Thanks in advance for any comments.................

 

The reason it "seems" to run fine are the knock sensors. They're retarding ignition timing when the engine is knocking,and before you can hear it. If it's stock-you really need to run at least 91 octane-relying on the knock sensors to retard timing is a risky practice,and can lead to broken ringlands or damaged valves from detonation.
JL

 

So should I be using 91 in my stock 03 expy with a 5.4l?

 

No,Expeditions with the 2V and 3V 5.4L are tuned for 87 from the factory. Navigators from '99-'04 are the 4V 5.4L, and are tuned for 91 octane from the factory. The '98 Navigators and a limited number of '99's are the 2V 5.4L,and those use 87 octane like the Expy does.
JL