Poor fuel mileage

[NWStroker01]

I read a thread a little while ago about a guy who was only getting 11-13 mpg because his truck was in safe mode. Anyone heard about this? I bought my truck new in 10/00 and it has always gotten 11-13 mpg, never seen better.
According to the thread the computer won't throw a code that OBDII type readers will see. So how do I find out? Thanks in advance, Kevin.

[djsdiesel]

is your speedo correct. If your like me w/ my 37's I'm 16% off. That can add up to 2 mpg. For example if your getting 13 mpg x 20 gal fuel=260 miles.
260 miles x 16%=301.6 miles 301.6 miles divided by 20 gallons = 15 mpg. Hope thats not too confusing. I thought I lost a crap load to when I put on my 37's but then I checked how far my speedo was off and calculted back. It made feel a lot better. I even had ford try to recalibrate my speedo, no go still off. Best thing to do is see if somebody has a GPS and check your speedo to that.

[Marty]

You have a lift, big tires, more air resistance and you're getting 12mpg... good job.

[NWStroker01]

Thanks for the replys fellas. Actually I've been getting this type of mileage frome the start, prior to lift/ tires/ Edge. Right after I bought the truck (new) I put 295/75/16 bfg KO's on with a level lift. Been getting the same mileage since then. About 2004, I was looking for better so I put in the intake and exhaust to help breathe better. Still no increase. Got about 50K miles off the bfg's, and decided to get bigger tires--went 35's. 2K miles ago I bought new tires and rims and bigger lift kit. All this and still no change in economy.

Which brings me back to the thread I was talking about with the "safe mode" in the computer that only allows you to get 11-13 mpg. I have friends with older PSD's that get near 20mpg with 35 inch tires, and was looking for the same.

Oh when I got the 37's I went to a speedometer shop and had the speedo calibrated on a dyno. It corrected the speedo/shift points,etc.

[NWStroker01]

When I went to 35's I had Ford recalibrate the speedo. After they did I kept blowing rear wheel speed sensors (like 3 times). I got po'd and had Ford recalibrate to stock and haven't blown a speed sensor since.