OK so we take a trip up to Miocqua WI. for the 4th and I get 6 mpg!!! when I first got the X with 17k mi. it would get 7.5 maybe 7.8 towing at 65mph. I could get 8 if I kept it at 60! over the last couple of years it has slowly declined to the point it`s at now. I always do atleast one hand calculation and compare it to the trucks trip computer it`s always +/- .1mpg., so I know everything is accurate. I have even checked my odometer against my GPS and again it was very close.
The only thing different this year is I replaced my "crappy for snow" Pirelli`s with a set of BFG AT T/A`s. now here is the part that may be an issue. I went from a 265 75 16 to a 285 75 16. both were load range "E". the overall tire diameter is only about 1/2" so the difference in tire diameter should be negligeable. like I said I checked my mileage both ways, odometer and gps and came out with a .2mpg difference with the new tires. I assume the additonal -.1mpg came from the slightly taller tire, for every 30 miles the truck is 1 mile slower than the GPS. but I still have 1.5 mpg not accounted for! I know the aggressive tread of the BFG will use more gas, but 1.5 mpg more?!!! and like I said I have slowly seen a decrease over the last couple of years. I have replaced the plugs (autolites), cleaned the MAF sensor and throttle body 2 weeks ago. and the last trip I still came up with the same mileage. so right now I`m stumped.
Maybe someone here has an idea!
Thanks!

 

BFG's are known for soft sidewalls and soft thread composition which will take away some mpg. If you have over 100-150K miles it would be a good idea to change the o2(s) sensor.


Make sure your tires are inflated to max pressure especially when towing. Lots if not most garages that install tires will only fill the tires to 60-70 psi. I have seen as low as 35psi on some of our trucks when they come back from getting new tires.

New 10% or higher ethanol gas also kills mpg. I have gotten my best mileage using shell gas. I will notice sometimes as high as -3mpg loss with cheap gas from places like BP (nothing against them because of the gulf deal) from what I normally get using shell.

The shell premium contains no ethanol and will yield the highest gas mileage but for a higher price for fuel.

 

Kevin,

I'm going to also go with the ethanol and other 'new' formulations these oil companies are using today.

I've noticed a BIG drop in mpg's just from the 10% ethanol in the V10...she really don't like that blend...I'm also noticing lower mpg's as a whole these last couple of years...My Ex has just less than 50K on the clock and still has the original tires...so that is one less variable in my equation...

My final answer is the gasoline blends are changing is the largest factor IMO.

Joe.

 

6 mpg while towing heavy loads with a gasser ?

I know...i know...this "mileage" subject has been so beaten to death I am almost embarssed responding to this guy.

Not sure how many times I have tried to explain the variables in driving conditions are so great, that no-one should be surprised at wide variations in mileage - even on the same road with the same load.

Bottom line. You want miles ? You got to have gallons.....!

 

Two different Excursions, my first a 2000, the second (my present one) a 2002- both 7.3 4x4's, both lost slightly over 1.5 mpg's when going from the stock 265's to BFG 285's. I like the way they look, handle, and ride, so the loss doesn't bother me.

 

Over 55 feet of fun has a price!

What gearing do you have? That low MPG sounds like 3.73 gears.

 

Shell premium isn't blended with ethanol?

 

Sorry not premium, V-power it is their 91 octane gas.

 

I didn't realize V-power isn't mixed with ethanol. Is this a state by state thing or is it across the board?

 

Like that one !!!!

 

I am unsure. I do know every shell I have visited in wisconsin has a sticker that says V-power contains NO ethanol. I use it for everything from outboard motors to my lawn mower. It is nice stuff, like what gas used to be like.

 

How heavy is the trailer? Do you use the tow button? I just got back with mine, towing 8500 lb enclosed ar trailer, 500 miles (420 with trailer hooked up), using tow haul (no 4th gear) and got a hand calculated 8.6, driving 65 mph or slower (depending on posting). I was happy with 8.6, my diesel would always get 11 mpg towing the same trailer. Do you take off easy or fast? Did you have a lot of stop and go at some point on the trip?

 

Oh, lucky you. The gas pumps here have stickers that say the "product may contain up to 10% ethanol" so I'm going to assume that all three grades have it. Shell V-Power is 93 octane here though.

 

Yes we have those stickers as well but at shell only the 87 and 89 octane fuels have that sticker, the V-power has the does not contain ethanol sticker. It is great gas for hot rods and high performance tunes.

 

Wish it was like that here in South Texas.

I've read that V-power is pretty much the same blend of fuel that Shell racing teams use in their cars so yeah, it's certainly a top notch fuel.