Recent fuel mileage drop
 

I have noticed a fuel mileage drop of about 3mpg as of late and was wondering if there is any wierdness going on with the fuel lately. I do not show any trouble codes, tire pressure is right where it has been for the last few years and the only real changes I have made to my truck have been the addition of new front springs and rearching of the rear springs that result in about a 1 to 1 1/2 inch lift and the new tires listed in my sig. My girlfriends Jeep CRD also has had a significant mileage drop. We use the Howes "meaner cleaner" as the fuel additive, any words of wisedom anyone might have as to a possible cause ?

You installed new wheels and tires....this could be your issue.

Just pushing 1 to 1-1/2" more air due to the lift is going to kill some mileage.

Also, you are correcting for the additional mileage traveled without you Odo showing it? For instance, my 97 runs 235-85-16's, which requires a 1.046 correction factor for miles traveled.

I lost about the same when I changed from old hard worn tires to fresh new soft tires. More rolling resistance... seems like it wouldn't matter but I lost 3 mpg.

I lost milage with the same size tires then changed gearing to 4.10:1 that help a little and was what I wanted for towing 5er

I talked with the guys at a local Cummins shop and when they heard that I had 247,000 miles on the original injectors, they thought that I might have some erosion going on with the injectors. No appreciable smoke at the tailpipe ( I ran 2% opacity at emissions in march) . The fact that it has been doggone HOT here I have been cranking the A/C and now most people ( that are not mechanics) are saying that must be the cause. Probably a bunch of little things adding up, most likely. Thanks for your opinions !

.................get ur valves adjusted...........kim.......

Valves were adjusted last spring. Running the A/C full tilt boogie this summer seems to be the most likely culprit. This is the first summer I've had A/C in about three or four years. Kinda nice !

when you run your heater in the winter the a/c comes on as well

Partially correct, the A/C compressor only comes on when you have your heater in the defrost mode.

I did not know that

Lurch, the A/C thing when defroster is on is true. I have heard two theories why. I give more credence to the first theory.

1 - the a/c makes the defroster run so that the seals in the a/c system don't dry up over the winter
2 - the a/c dehumidifies the air (which makes sense) so that the defroster doesn't have to work as hard to keep the windows from fogging up / frosting up.

I have never been totally sure why the system is built this way, but it has been like that in any car or truck I have ever had that had a/c.

Ding Ding Ding, we have a winner Johnny!!!!!!!

99 dodge 2500 5.9. Hard shift into 3rd
 

While driving if I slowly increase to 45-50 mph when it shifts it tends to roll a ton of smoke if I'm trying to accelerate quickly. Any thoughts?