I am not quite sure if it is because of the performance upgrades or not, but my gas milage is going down hill. I have put in a K&N filter with a Velocity Tube, Flowmaster "Y" to single 3" through a Gibson muffler and a Superchip managing it all. My gas milage has gone from 14-15 in town to around 12-13. I don't drive it like I stole it since I put on the performance gear, I still drive the same. My only other guess would be something in the tranny since it also had a shudder problem resolved at Ford with a flush and fill at about the same time or possibly some kind of sensor like O2 or something. No engine light though. Any thoughts??

 

My guess is that these mods are for increasing power in the "higher" rpm range. You may have actually lost some power in the "lower" rpm range. So, in order to get the truck moving, you have to give it more gas, thus using more.

Another possibility is that your computer has not "reset" itself yet. It usually takes 100 miles or so to get it working well with the mods. What you really should do is reset it again, and then "drive it like you stole it" for a short period of time (just watch out for the cops!). And mix in some normal driving too.

I don't have all the mods you do, but I did notice that after I did the reset after installing my K&N drop in filter and the Gibson SS exhaust, it took some time before I saw my mileage "stablize". I'm getting around 14-15 average with 75% of this being highway miles. My mileage will really suck if I'm stuck in traffic or do alot of short trips. My best mileage was 16.5 mpg on a 400 mile round trip in one day.

 

What engine do you have? I have the 4.6 and the best I have got for city driving is 12.9. That was before and after the mods. I though about changing the O2 sensors.

 

Same result with my mods. Horsepower isn't free!

 

I don't think it is because of the need to give more gas to get the truck going. I feels to me like it needs less gas given. I also don't think it is because of the computer reset. The mods are atleast 3 months old. I have the 4.6 V-8. My engine light just came on this week so hopefully that will fix the problem. I will keep you informed. With all the mods I have performed, every one claimed better gas milage and I figured I would atleast get some better.

 

its due to the ole LED FOOT!

 

Colder temps---higher rpms---thicker oil---lower tire/air psi---longer warm-up? Saw you are in Idaho--how cold is it?

I have similar mods on my 97 4.6 f150 xlt and my mpgs went up by about 1.5 to 2 mpg. I think yours should go up slightly too.

Dan

 

I have almost the exact same mods as you and my gas mileage has improved a little. Most noticeably after the superchip.

 

I'm going on 7-8 months with all the performance mods (not like it's a lot) but my milage has gotten consistantly better. Now that it's getting cooler, I'm easily getting 1-1.5 better around town. I'm getting about 14.5 right now and that's combined with towing my 7000+ pound boat around on the weekends. About 20% of the miles since I've reset the overhead.

Without any towing mixed in, I'm getting 15 or so around town and 18-19 HWY although I haven't done any road trips since it's cooled down. If I reset on the hwy and check pure 60-75 MPH hwy driving, it's anywhere from 20-22.