Ive been running 87 octane in my 2000 F-150 reg cab short bed 5.4 4x4, Im a lead foot in the truest sense of the word, and My mileage still ran at about 14.5 mpg per tank about 60/40 split freeway/street, one day I got a $60 gas card from work and filled up with premium, truck seemed to like the extra octane and almost seemed like it was running on less fuel, did not realize i went 438 miles on 24 gallons, just over 18mpg. I was in gas pump shock! No more 87 for my 5.4. 91 all the way.



P.S just broke 90,000 miles and she still runs like a dream, recently had to replace front brakes, but after 5 years and 90,000 miles. Blue oval all the way!

 

Your right most people do not believe the higher the octane the better the gas mileage.

Just taking about it the other day - see attached link
https://www.ford-trucks.com/forums/s...d.php?t=352056

The ratings on pump gas is the highest it possibly can be.

Rating 87 octane - can be 86 to 87 octane.
Rating 89 octane - can be 88 to 89 octane.
Rating 91 octane - can be 90 to 91 octane.

When buying 87 octane that is the highest the octane can be. You could be pumping in 86 octane. That why I buy 89 octane most of the time. This way I know I my getting at least 88 octane.
When on the road I pump in 91 octane and my miles per gallon go up.

Maybe this is why people are blowing there plugs out of the heads. Should
do a survey and see what octane they are using.

 

Use only what the manufacturer says to use.
If it's 87 use it. The computer on your truck is designed to use only that, anything else is supposed to be a waste.
Mine is 87. Studies have been done before and proved that.
That's like oil....The oem says 5w30 and that's EXACTLY what I have used and with 212000 miles it must be working ok.

 

This is interesting, care to explain this theory?
Have you determined that the increased MPG is ofset by the increase of the price per gallon?