My truck is getting extremely poor fuel mileage. It's in the 13's driving around town (before exhaust change out), and being an electrical contractor, that's the only place I drive. I'm wondering if the trans TC is so sloppy that I'm spending most of my time spinning up the engine, and less time actually moving.

The truck has about 130k on it. I get just the tiniest hint (hardly visible unless you're really looking for it) of black smoke if I punch it from a stop. I've cleaned the pre-filter strainer, but it was already spotless. The truck is really a pig if I'm accelerating from a stop up any sort of hill (real slow to spool up). The exhaust is real stinky, (worse than what I remember a year ago) until it warms up after a few minutes of driving, first thing in the morning. I always thought this was normal, but now with my lousy mileage, I'm wondering if I have injector problems. For kicks, I replaced the stock overflow valve a few months ago. The truck doesn't show any of the symptoms that I've heard of to indicate the timing has slipped. I'm going to have a guy in Downey bump it to 15.5 just for good measure though.

Basically, I have to get this mileage situation fixed before anything. My money is just going out the exhaust because of the bad mileage. In due time, I'll also get the transmission sloppiness taken care of. For all I know, it's the trans TC that is causing the problem, but I don't want to get it all fixed up and find out the mileage is still in the tank. Spending money on the transmission will have to come after I'm able to save some money on the fuel, unless it's the transmission that is causing it in the first place.

Thanks for the advice.

OK, I'm off to work. I'm just finishing up my second week of self-employment, so until I get some money flowing a little better, the only days I take off now, are Sundays. That's why I have to get this fuel mileage thing fixed!

 

Don't know, but to me, that sounds nearly right. My around town is about 15 -16.5 with that being rural roads and small town traffic. That is also with nearly empty pickup weight as a daily driver. Loaded or with the trailers, it drops to about 13 or slightly less.

Are you driving with the overdrive off? Mine does better if I keep it off whenever I'm under about 45 mph.

I'm interested to see other comments.

Ed

 

Sounds low to me

I think u mean NP 241 transfer case? oh well i could be wrong, which has happened a time or two he he he he he he, well anyways, whatever the case maybe, your mileage seems low to me, but i have no experience with the auto tranny, but i would check ur filter just to make sure that it is clean, and start using some additive, if it shifts (the tranny) into overdrive at 45mph, id say lock out overdrive too..

Tx

 

The first thing I do when I start out, is to turn OD off. I don't allow OD until 55. I thought that was common practice among everybody.

I'm not sure what you're trying to say TxDiesel007. By trans TC, I am referring to the torque converter. By NV241 in my signature, I am referring to New Venture Gear 241, not New Process Gear. It's all the same really, but I thought it had been quite a while since the company referred to their products as an NPxxx. Filter, additive? I'm assuming you're referring to fuel, in which case, the fuel filter is clean, and I'll use a slug of Power Service Diesel Kleen every second or third tank. No difference whatsoever. If you are in fact referring to the tranny, well, unless it were the consistency of tooth paste, the oil shouldn't really affect my mileage, should it?

 

Why would you? I don't do that, never have.

The mods in my sig pushed me up from the fuel mileage you are seeing, to a consistent average in the 16's.

 

Well, I had this big explanation typed out, and then realized there are some things that can't be described, only experienced.

 

A tighter TC will help. Stock TCs are sloppy junk. Having the O/D locked out, in town, is a good idea with 3.55 gears.

NV241 t-case is correct.

My engine mods brought my mileage up, by 1.5-2mpg. Your mileage sounds low to me also.

Do you have a lot of idle time?

If you still have a cat. convertor, it may be getting plugged with soot. Any exhaust restrictions will hurt your engine and performance. Check/replace your air filter.

Check the fuel injection pump timing.

Check the fuel pressure.

Is the shut-off solenoid coming up all the way?

http://www.dieselpage.com/tips.htm

 

Start by ditching the cat. I went from 14 in town to 16-17 in town with a 5 spd, 4.10 gears, 4x4, and a 105 gallon farm fuel tank in the back I always haul around. My boost also went up 10 psi when I strait piped it.

 

Do you really think I still have a cat? I've got a 4" exhaust from stock down pipe back and a 30" magnaflow for crying out loud.

No idle time, other than slow traffic on the freeways or idling at stop lights.

 

You say you have a service body on it, so I assume you are carrying around a bunch of iron some of us call tools. Have any idea of the weight? If you are loaded like my service truck, you will want to inflate your tires to max psi. If you are getting stinky smokey exhaust when you start it up now in the summer for a bit, you may have late timing or leaky injectors. You say you use fuel conditioner every third tank or so, so I would guess that if timing doesn't improve things you should have your injectors pop tested. I think that the oil companies are playing games with the fuel again, my truck has irratic fuel economy from different stations. You live in a privelaged state with "special" fuel requirements, so you may be experiencing the results of that.

 

For 100% stop and go traffic driving with several on/off cycles thoughout the day I don't think 13MPG's is completely unreasonable depending on how loaded down your truck is with tools and/or if you are towing a trailer.

Maybe and exhuast leak or stuck WG are why your truck is slow to spool while accellerating from a stop up a hill.

You are correct in not running OD around town so that is not your problem.

Do you have a fuel leak?

 

I must be lucky. Checked every tank, 264,000, 18 miles per gallon, every once in awhile a lower reading. After using Lucas fuel treatment I now get 20 even. 90% highway, only carrying a couple hundred pounds. Bone stock except for BHAF. And a 47-RH auto with a stock TC thats very sloppy. I've noticed these engines are very sensitive to change, even when the oil reaches 3000 miles the engine begins to vibrate differently. Just ran up and down the White Mountains including Kancamagus Highway, 415 miles, 22 gallons used.

 

I finished my gauge installation this last weekend, and I think I figured out why my mileage is so low. Because my torque converter is stock, my engine revs to 2250 when accelerating from a stop. My truck slowly catches up to the engine. My turbo is going to full boost (stock 18 psi). You can't make boost without fuel, so obviously the fuel is burning like crazy when accelerating. With a tigher torque converter, I wouldn't need to give as much throttle in order to acclerate. I guess it's time to take the plunge and get a performance transmission. It will pay for itself in fuel savings, eventually.

 

I found an improvement when my new TC was installed. Recently checked mileage around town altho not all stop and go and averaged 18,6.
During this check I made an effort to drive for economy.
Bet you'll see improvement with better convertor.

 

It seems like you should see an increase in around town driving MPG's with a better TC but don't expect much. I was hoping to get an MPG increase but it did not happen.