I have some good news! I have always used the cheap ARCO 87 gas and switched to mobile. I was getting 14.5 on average, on the last 3 fills with arco. I changed to mobile 87 and it jumped to 17.2!!!! I've filled up again with mobile and will post the numbers. Then I will try 91 after that and see.

edit: I'd say the price difference is less than $2.
- roughly a .10 difference between 87 arco and mobile.
- fill up is around 15.5 gallons on average, so .10x15.5= $1.55
- roughly, I'm getting 35 miles more for that $1.55

in summary, I'm paying $1.55 more for mobile fill up and getting about 35 miles more on each fill.

 

i have tried about everything too. replaced everything, tuned up everything, synthetic in all gearboxes. i did notice for some reason after changing my o2 sensor that for the first two tanks i got the same mileage, but from the third on i have gotten about 35 extra miles to the tank. i run 33x10.50's and get 285-305 miles out of a tank. ive also tried driving grandma style. honestly i got better mileage when i stay in fourth gear a lot and only use 5th downhill and on really flat areas. i need to regear soon, but from my experience driving easy doesnt help my mileage at all.

 

driving easy doesn't seem to help mine either. I drive about 50% highway and 50% city. The highway driving is not stop and go L.A. traffic either. its smoth long 40mph roads and then 2 or 3 stop signs to get from point A to point B (i drive the same route 90% of the time).

I have 265/75/16 pro comp MTs and Im not geared. I use only chevron 87 with techron. K&N air filter, synthetic oils, etc. No intake or exhaust mods yet. I get about 12-13 mpg without factoring in my tire size. about 13-14 mpg after factoring it in and I drive pretty average. I'm not as spirited as i used to be but i noticed that it doesn't help unless your flooring it close to red-line all the time. im hoping my o2 sensor, spark plugs, fuel fuel filter and deckplate mod + exhaust will help it just a tad.. it'd be really awsome to get 16-18 mpg.

 

A question about gas quality...how does costco gas measure up to exxon or other name brands...does anyone know what gas they have in thier pumps? Thanks

 

prolly the same gas...only a few people actually know what brand their fuel tanks have in it. i use costco most of the time because of price.

i remeber a study/survey? done a while back and they found that most of the smaller stations had the same gas in them and had paid different prices for it.

 

Did a full tank, highway speeds only, and got an amazing 16.3 mpg this weekend. That was also traveling pretty quickly (75+) most of the way.

 

what scanner do you have and how much, can i rent this from somewhere?

 

MTL_4Runner is right on the mark. I drove over a mountian pass (Portland over Mt. Hood to Bend, OR) and made 23mpg, tires at 37psi, 4.30 stock gearing and I guess I should add that I run street type All Season tires on my stock alloy's for road trips. I actually used cruise control and kept the RPM's at about 2000 or as close as possible. Other specs, auto tranny on 2000 4Runner mobil 1 oil in motor, dino otherwise, stock air filter, new plugs and wires at 80k/miles, frequent air filter change (at least every 15k), rig now has about 108k/miles.