I have read in the owners manual for my 21 f150 3.5 Ecoboost that it is recommended to use 91 octane, although 87 will work. Does anyone use 91 and notice a difference?

 

foud another post about it. this can be deleted.

 

I use 87 with no problem getting 20 MPG. Tried 89 a cpl tanks didnt notice a difference in power or mileage. I'm at sea level.

 

I had no problem getting 20 MPG on 87 either and I’ve always run 87 in my vehicles. But I must say running 91 or 93 makes a noticeable difference with my 3.5. I would say it’s a slight improvement in MPG probably not enough to justify the cost but it just performs better and that makes it worth it to me.

 

My truck is still fairly new around them 620 miles. Locally I can get 90 octane ethanol free that is my main choice of fuel. It is about the same price is premium 91 octane or higher.

When I can’t get ethanol free, I do prefer to run premium. The additive packages are better and yes, the cost is slightly higher, I feel better edit additional mileage creates it to be a benefit for me

 

you regularly run rec fuel in your truck?? why would you do that? that's for stuff like boats and atvs and not normally meant for passenger car use. the 1 time I accidentally put it in my truck it ran like crap till it was gone.

 

Fuel is a BIG subject most never hear about or understand.
All heard is 87, 91, 93, E85, E10 etc but never what's in the mix and what the engine program has to do to adjust to a change and how long it takes that change to stabilize before making judgements. The adjustment comes from the Ox Sensors >>over time. They detect what Ox is in the exhaust from anything that is put in the tank and send that info to the program were the changes are made until a stable condition is reached.
What is thought of as a simple fill at the pumps with a different grade or even a different supply name is complex.
Good luck.

 

It seems it makes adjustments rather quickly to me. Kind of surprised me that I noticed a difference in just a few miles from switching to 93 from 87.

 

well clearly you mistook the effects. I can guarantee you would get more range & mpg from Eth Free than 87 E10.
Rec fuel in most certainly street legal... its not like Off Road Diesel.

 

89 is complete trash. If you're going to be in boost... super unleaded in the 93 octane flavor will keep the knock sensors at bay and you'll get all the ignition timing your truck was tuned for.
You understand what turbochargers do... right? Last thing you want on a boosted engine is low octane swill.