I know the 07+ 5.4 3 valve engines were tuned for 87 Octane fuel. The 05-06 were tuned for 91+ and that is what I put in mine for the final 210k miles of it’s life before the accident. The fuel mileage was totally ethanol percentage related. We bought fuel on a trip in Wyoming that only had ethanol free fuel and the mileage bounced back to the 18 it got when new for that tank. The next tank was back to the dreaded E10 and it went back to the usual 14-15 it would get. This was at normal highway cruise speed of 75-80mph. It does a little better under 70 but who has time to do that.
Reduction in MPG
- Thread starter Gary Waugh
- Start date
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Go for it! I also have a bridge for sale. Oh, that confidence is based on 40 years in the trade, not some clown with a utube channel trying to sell stuff.
17expi
Well-Known Member
O P; I wouldn't worry about it, it's just a malfunction somewhere, but check your plugs to see if it's running too rich.
