View Full Version : dropping fuel mileage - help!

12-05-2002, 10:05 PM
Truck purchased new in sept 2000, presently just over 25000 miles, light usage with minimul towing and 99% city driving. Mileage has dropped from high 13's and 14's to 10 to 11 mpg.<br>I have kept track of every fill up since truck was purchased and this is the worst its ever been -taking into consideration time of year and cold temperatures. I haven't noticed any change in performance or power and driving habits are pretty standard. The dealership tells me there is a long breakin for cummins but shouldn't mileage be a little better than this and not droping? Highest mileage on highway 65-70 mph was 18 over a year ago with the most recent at 15.5 mpg 200 mile run. Rear end is Dana 3:55 with the 4sp. auto. transmission. I have been considering buying the edge ez performance booster to help mileage but I'd like to know if I have other problems I need to deal with first. Any advice from those of you that may have experienced this problem with the cummins and input on the power boosters will be most appreciated<br>

12-05-2002, 10:09 PM
Heres things to check, Air pressure in tires, fuel filter,air filter,and reset your APPS. this might help.Also this time of year blended fuel doesn`t help.<br> Danny

12-05-2002, 10:20 PM
Jon, base stock gear oil gets awfully &quot;sticky&quot; when it's cold, and can really cause a drag on your drive train. You might consider switching to a synthetic in your differentials. I've been getting slightly better mileage than you at around 17-17.5 (calculated) doing 95% interstate driving. Any type of stop and go driving beats down the average real quick. In the summer, with unblended fuel, my mileage was around 21 for the same type of driving.

&lt;edit&gt; There's a lot of info on fueling boxes available on the forum and can be accessed by a search, but you should be looking at gauges and transmission upgrades if you intend on adding a box. Boxes usually make short work of the stock tranny.

12-07-2002, 12:19 AM
thanks for the info on the apps sensor - makes sense for the problems and could definitely be tied to decreasing fuel mileage. dealer has messed with tranny adjustment half a dozen times in the past year to get an acceptable shift pattern and just maybe - something else got adjusted too!To much complicated b.s. for a strong simple engine. Anyway I'm taking it in for service next week - we'll see what they can do this time and I'll pass it on. thanks again.

Hired Gun
12-07-2002, 01:36 PM
Cattle Hauler and I were discussing the same thing. I mentioned the APPS thing. Neither of us know exactly what you are talking about. Please fill us in?

12-08-2002, 12:46 AM
OK know about the apps but cannot remember how to reset it.anybody care to refresh my failing mind. ::) <br><br><br> Mike

12-08-2002, 12:54 AM
disconnect batterys for min 30 minutes (neg term)
reconnect batterys turn key to on
push pedal to floor, let off slowly turn key off
Your done.

Push Rod
12-08-2002, 08:29 AM
In addition to the good advice thus far, I'd check your fuel pressures. One symptom of a failed lift pump is poor fuel economy. <br><br>Rod