Premium fuel =less mpg.

[WeekendPlinker]

With regular unleaded I average 14.5-15 mpg city.

Have filled up with premium twice now and I'm only averaging 11.5-12.5 mpg.

Isn't this bass ackwards??

 

[BRUTUS_T_HOG]

Seems odd.

Consider how much longer premium fuel sits in the tank at the gas station vs regular. Maybe the fuel is contaminated/stagnant.

 

[02 Burb]

That makes sense if your vehicle takes regular, higher octane doesn't always mean better. For our trucks the timing is made for 87 octane, running 91 will only cause the engine to run rich resulting in lower mileage and more fuel burnt.

 

[Rangel]

yep I ran a tank in both of my nnbs and both mileage dropped with the supreme tank.

 

[humer101]

If you truck engine is set for 87 down gasoline, so you do not put 92 or high, if you truck has a yellow gas cap that mean you ignition timing is way down , when you use 92 plus gas is not going to work right. you have to tune the engine and you see the difference.

 

[Mister H12]

No no no! You did it wrong!! Black Bear tune... THEN premium fuel!! Lol

 

[humer101]

Yep

 

[Big Buttons]

No no no! You did it wrong!! Black Bear tune... THEN premium fuel!! Lol

This ^^^

 

[WeekendPlinker]

No no no! You did it wrong!! Black Bear tune... THEN premium fuel!! Lol

This ^^^

It's a 02 Yukon with the 4.8 with 152xxx miles. Would the bb tune be worth it to do now???

In a year or two I plan on doing a 6.0 swap will the tune still work when I do that?

---------- Post added at 03:16 PM ---------- Previous post was at 02:52 PM ----------

I had a "fuel mileage plus" additive added to my fuel for 10.00 when I filled up at a Murphy USA in Mississippi a few months back. My truck got 22mpg highway with that additive. The next fill up was just regular gasoline and the other half of the trip I only averaged around 17mpg.
Any idea what kind of additive can boost mileage like that???

 

[TraumaTruck1]

The 6.0 would take a different CPM, so one tune would not work for the 2 different engines.