usmarine0905

Hi, my 98 C2500,5.7 Vortec,auto. great truck, bad milage. I have done all that I think i can to improve it, all filters,plugs,wires,cap,rotor. I even replaced ujoints to free up rotation. Is it that the 2500 just is mainly a work truck and milage is not important? LOL. I use it mainly for traveling....

and one other thing,, the heater motor (Blower) It has one speed HIGH, would that be the motor or the switch? and when it rains water settles in the motor housing, any ideas where it may be coming from?

Thanks to all...........

maxxman04

what kind of mileage are you gettin? extended cab, std cab? these trucks aren't really known for economy. i'd say if you're gettin anything above 13 or 14, you're probably ok. you might try seafoam injector cleaner (that is the name of it) get it at parts stores usually. also, have trans flushed, trans filter changed.

usmarine0905

Yea it's ext cab. that is above what Im getting, 11-14 mpg. seafoam I will get some and try it to clean the injectors. I guess the 2500 is a real work truck huh...LOL. trans filter and flush, next weekend sounds good. thanks

maxxman04

auto trans on average, when in top shape, have a 7-10 percent slip rate. as fluid gets worn down, that number goes up, meaning it takes more power, rpm's to turn trans. this difference you will never notice, unless there's serious issues, except in fuel economy. use quality filter, quality fluid, maybe even a high mileage synthetic if you're above 75k or so on truck. also, use quality ignition parts. brass contact cap/rotor, good plugs, wires are a must, low resistance wires. some here might say stick with delco all the way, i personally run taylor spiro pro on my rigs. you should be able to see 11-14 city, up to 17 or so on highway, maybe better if everything is good. good luck, keep us posted.

therewolf

I use my 2500 for travel.

A cover on the bed will give you 2.5-3 MPG. My big gas saver on the road and around town was a gear swap out from 410s to 342s.

Lowered my highway revs by over 1000RPMs, and doubled my city MPG.

Polk540

Double really? wow.What mileage were you getting before and after the gear swap?

therewolf

At the time of the gear swap, my highway MPG (with a fiberglass cap) was @14.5 MPG.
My mileage just after the swap was just a hair under 18MPG. (Not bad for this behemoth!)

As to city driving, I'm sure it was something awful, but I never checked actual MPG that closely. I calculate it by fill-up frequency. I used to get a fill-up weekly,more often if I did "run&gun". Now I fill up every two weeks. Ergo, I "doubled" my mileage.

The effect of the swap has been to drop revs dramatically. What I've lost in low end power I've more than compensated for in fuel savings. But if you have 373s, it wouldn't be worth it to go to 342s.You'd have to make the jump to 323s, which could defeat your purpose in having a pickup, if you need low-end jump, now and then.What's your gear ratio?

usmarine0905

I have the GT4 code.... 3.73's I dont do any hauling just driving. so I dont really need the low torque. But if the cost is that far there to switch them, i might just keep what I have...

maxxman04

keep the 3.73's. it's not worth what you'll lose by changing.

Polk540

3.73= Cruising gears anything less and your truck really isn't a truck.Mine is 3.73 and I got 17mpg highway on the way to El Centro From Lemoore last weekend.Took a whole tank cause I was doing 80.On the way back I was loaded down and slowed down to an avg of about 70, didn't hit the low fuel light on the way back so might be 18-20 mpg as I still supposedly have a 1/4 tank left.lol.