I have an 03 Screw 4.6 V8, 4X2, XLT, and i used to fill up using either diamond shamrock or amoco since i bought the thing in nov of 03, well i just got a shell gas card so i could establish credit, and now i use the shell but i have noticed the most horrible gas mileage now from shell, like ill fill up and it fells like a smoother drive but the mileage is like at 90 miles when the tank hits a quarter tank already burnt, is it maybe because i went from one station to another? i heard that is bad, though i let the tank basically dry before i started using shell, so the gas wouldnt mix, hmm wonder if i should go back to shamrock, anyone else have this problem?

 

How many miles do you have on the truck? Is the maintenance up to date (specificly the fuel filter)? I mix gas brands all the time, never had a problem. I usually use up the tank before refilling too. What was the MPG you were getting before? I get about 15 MPG with about 75% city/25% highway driving, but I have the 5.4 engine in a supercab.

 

I have a 98 4X4 with 102,000miles, and average 16 mpg highway.

 

I have noticed a difference while others claim there is no difference in brands
I have been running texaco 93 and been getting better milage about 18.5 mostly highway but drops to 15.5 if any city and or air on.
02 5.4 4x4 scab 3.55 265/70/17under drive pulleys k+n and Preditor
over 380 miles per tank and not at low lite. Texaco not very common station around here.

 

My guess as to the slighly lower number is they are adding alcohol about 5-10% to the fuel. This will not hurt your truck and may in fact clean the insides for ya. However you will get 2-5% less milage.

 

I track every fill up in my truck by octain and brand. Without fail, I ALWAYS get 2-3 more miles to the gallon when I use Shell. Amaco gives me the worst mileage, by a lot, and Mobil come somewhere in between.

I don't like diamond shamarock because by engine runs pretty badly with their gas for some reason.

 

Same here, Shell gives me a slight boost in mpg. I usually buy either shell or cosco gas whichever I happen to be closer to when Im running low.