Ok guys need some help here.I have a Red 98 12V CC when I first got the truck it got 15.1 mpg the 2nd time only got 13.1 now this time 13.06. what's going on guys need help with this situation. Thanks Cin

 

On the same subject...I am a little dissapointed mine did not get better after some recent mods. I just timed mine at 16*, valves adjusted, overflow valve, added 4" exhaust, synthetic fluids all the way, and for the month of May I drove it 1000 miles and got 15.2 mpg . (That is not corrected for my 285 tires, so maybe its around 16.5 or so) I was thinking it would be a little better though . It sure is running good though and maybe I've had too much fun with the go pedal !

 

I know the feeling about the running good part. Don't get me wrong I'm not mad at my truck or anything like that LOL. I run in the city quite abit maybe that's whats wrong with mine.

 

4.10s or 3.55s? Heavy truck in town driving is worst case scenario for mileage. Is the trans slipping any? Fueling plate makes truck more fun but increased power means increased fuel consumption. Tires properly inflated? Alignment good (tire wear equals drag)? Lots of little things can add up. Like fan clutch staying locked up. Could also be dirty fuel filter causing unnoticed loss of power so you are using more pedal to compensate (although some people would say that driving a big stinky diesel pickup is compensation for other shortcomings ).

No one solution, probably. But some of the fun is figuring out what is causing it.

 

I was getting 21 mpg, but since I have started leaving the overdrive off until highway speeds I am getting 16 mpg. I have to admit though, my truck is quite a bit more responsive with the overdrive off and I have been taking advantage of that at the stop lights. I seem to be getting to work a bit quicker

The good thing is it gives me time to let the turbo cool down before I shut it off.

 

I think the in town driving is one of the problems and my #8 fuel plate is other problem. Everything else has been done to the truck. Thank you all for the help . Cin

 

I get 22 or 22.5 on a freeway trip, empty, and 20 with mixed in-town driving, and always wait for 50+ MPH to engage OD. Your low milage must be a combination of inefficient injectors, #8 plate, and your foot. Does it smoke heavily? That's just wasted fuel. Also, since your driving is mostly in-town, see if your auto tranny is just churning all the time and not providing a good connection to your wheels.

 

My wife's 98 gets around 17.5 all the time. Pretty much stock.

..Preston..

 

I manage to only get about 14.5 on the road empty (running 75 or so) and about 12.5 pulling my tractor on my trailer which weighs about 16,000 pounds (running about 70 or so). I used to get better mpg before mods, but I couldn't run over 100 pulling 16k then either.

 

my truck is the complete opposite of most. i get better mpg in town than running 70 on the free way. idk why but it does. also it smokes more in town then on the road for some reason. but thats most of the problem with mpg is ur foot.

 

Ok guys No it's not my foot! and I have new injectors. I would not even ask about my MPG if in fact I knew I was doing something myself. Now I already know about a lead foot and I would expect that. That is not the issue. Thank you Cin

 

I have a 97 with all the mods in my sig. When I am in toun only I get 15-16 mpg . On the highway I get 18-19 when I pull my 14k 5th wheel I am getting 10mpg. Before I slid my 10 plate forward and installed the 215hp injectors I would get 16-17 in town,21-22 on the highway and 12-13 pulling my trailer.I am going to get a snow water injection system and see if the milage comes back. If it doesn`t I might move the plate back and see what happens. If that still doesn`t do it I will put my stock injectors back in.

 

Have you checked the air filter? I had a K&N on my Excursion get pretty dirty and found about 1/2 a MPG by doing the overdue service. They need lots of air, to run on the lean side.

 

I have a new Stage1 AFE filter

 

Could be fuel quality. I live in Ft. Worth, Tx. and the fuel quality sucks, I'm only gettin 15.3 in city with my '98 12v 4x4 5spd. but I fueled up in weatherford west of Ft. Worth and got 18 mpg in city and 23 on highway. Quality is a big factor when it comes to MPG & POWER. By the way I run 285's.