Good info...so here is another question.

What about those of us that have a chip programmer and we have it set at the high performance setting that the programmer says requires at least 91 Octane?

Does this fall under the same rule as advanced timing?

 

Yes the tuner among other things advances timing when selecting a tune for higher octane fuel.

 

That is what I suspected but I was not sure.

Thanks!

 

Just remember, my response was specifically in reference to the V6 motors. And in particular the two in my driveway which are supposed to be identical, but definitely not.

 

Theoretically you could actually get decreased gas mileage with an octane level higher than what your vehicle requires. As long as your engine is not pre-detonating, the lower octane's hotter burn (smaller octane chains burn faster) should give you a bit higher horsepower. I say "theoretically" because this is the case with my snowmobile. According to the Arctic Cat engineer who designed the engine with Suzuki, I get a couple horsepower higher burning 87 than burning 92. In fact he said the engine was designed for 85 octane and would generate the most horsepower there. If the logic transfers to a four-stroke truck engine, well then you're worse off power-wise with higher octane gas then Ford recommends (for a stock engine).

 

Interesting thread. I just ran a tank of 91 to see if there would be any difference in my 05 Screw 5.4L. No data to show, but seems to run the except the mileage was only marginally better. I will go back to the 87.

 

Congrats on your two factory freak V6's.....


Your fuel doesn't care if you have 6 cylinders or 18 cylinders. There are laws of physics that govern how much power your engine makes. Simply putting a higher octane fuel will not increase performance unless tuned for it, plain and simple. You made reference to checking the timing. Can you data log the timing under driving conditions? Can you monitor A/F ratio? Can you log calculated load? Torque? Any of these things can help support your argument. Remember, these trucks learn your driving style. If your son beats on his truck more than you do, it is going to run a little more aggressively. I don't think that the stock computer has the ability to add enough aggressiveness that having higher octane fuel would make a difference.

 

No, no tuning equipment. But just for amusement, my truck is on 1/8 tank and boat is covered for now. I'm going out to get BP 87 which is exactly what Ford recommends and will see if the miss and sluggish performance return, as well as to see if the 87 wizzes through like a urinal, which is another issue. The only thing is it really takes two tanks to get a fair trial, but lets see what happens. I will document any changes exactly and report back from the "seat of my pants". However, despite the lack of computerized equipment, I think I'll be able to tell if it runs lousy.

 

Sounds good, MisterDave2, I'm very interested to see the results!

 

OK step 1.
15.4 gal of 87 Sunoco to top off my truck from the 89
12.2 gal of same to top off my son's from the 93 BP
BP station was getting delivery and everything was screwed up and I had to go to work so Sunoco will be just fine for comparison, it's the fuel of NASCAR......
There will be no BS, just the straight facts of what does or doesn't happen through two tanks, I even plan on towing the boat up the hill next week.

 

don't change octane; change gas stations

 

Last Friday, when i filled up from empty with 91 instead or 87 (edge was due in) i noticed i little bit more pep off the line but that's it. it could be just the fact that the 91 was still the summer blend and 87 has long since been winter blend. In the fall i could really feel the difference which gas stations switched. The only reason i ran 91 this tank was for the edge, now it actually feels like I'm driving a 300+hp truck i love that little box
Ps. I don't know about millage but assuming it's gonna be lower due to driving it harder

 

OK so I'm about 25 miles into this gas since Saturday. Cold idle which is usually nice and smooth with maybe a little bump around is now more pronounced with multiple bumps. Once it warms it seems to go away. It also is self adjusting its cold idle more than usual up-down is more pronounced, 89 just starts and runs steady withour much fluxuation. Middle of the pedal is a little less peppy. From a dead stop feels similar, middle range of pedal is kind of shy until I push it down further to force a gear change. Again, none of this is a big change, just some small stuff, but it's different.

 

Disclaimer: I am not a mechanic.

I don't think any fuel (brand or octane) increases actual performance. From my experience, newer vehicles run great on any type/brand of gas as long as octane recommendations are followed. But once you get over 100,000 miles the difference between brands and octane levels become more prevailent, maybe making the engines run a little better or smoother but still not increase performance.

My trusty mechanic told me pinging, especially knocking, is the number one cause of engine damage. So I use the lowest octane that will not cause "pinging" in my engine, which is 89.

 

Fuel octane will make a performace difference when the engine is built for hi comression. Timing has to be adjusted. An old 78 F-150 would run alot better with some 104 octane vs 87 but the base timing has to be set from 10btdc to around 18-20 btdc. The newer OBD II systems are set from the factory with a base timing and fuel curve for a certain octane. The only way you could tell a difference in the vehicle is to be switching from a 87 winter blend to maybe 93 octane that is still summer blend which has been sitting in the tank at station for a while. Winter blend gas starts to lose octane within 20 days of sitting. So if your truck is going to sit for a while and you have winter gas put some stabil in that hog.