Any ideas what could be causing bad gas mileage? I have a 06 350 SRW 4x4 SB PSD with about 70,000 miles. I clean my air filter every time I change the oil and had the fuel filters replaced around 15,000 miles ago. It seems I get around 8-10 mpg regularly, granted I do most city driving. But even hwy driving I don't get much better. I know this is a vague question since mpg differs depending on driving habits, but I drive like a grandpa.

I use the truck mostly for hauling my 40ft fifth wheel and get around 8-10 mpg when towing. This seems odd I get the same mpg's when not towing. Anyone have any suggestions on if there's something specific that can cause this? I've had the truck for about 3 yrs. When I bought the truck it had a 8" lift with 37" tires and I got around 16 mpg. When I removed the lift and put 33" tires I noticed the gas mileage decrease a little but seems to have got worse over the course of the last few months.

Thanks for any suggestions.

Tim

 

It may be worth noting that I have an AirRaid intake and a Banks system in addition to a 4" exhaust. And also I noticed the fuel economy decrease mostly after I moved to California. Don't know if CA uses a different blend of diesel, but after reading other threads, it seems that's what some people think. Hell, I may have just answered my own question. I just hope there's something like a software upgrade or something along those lines that will help. If not, then I guess it is what it is.

 

I would get 14 in mixed driving in San Diego, I would get 16 on the HWY. City, well that depends on how many lights I hit in any given day.

Yes I would get another MPG if I used Arizona Diesel. Truck would run better also.

10 on the HWY is BAD, worst then my V10 which is known for Like gas.

 

Check to make sure that you do not have any brakes dragging. Just feel each wheel rim to see if any one (or two) are warmer than the rest.

Sticking calipers or slide pins can cause this sort of problem. The fix is relatively easy.

Lou Braun

 

Was the pcm reflashed after you took the lift and big tires off? It probably was reflashed when they were put on.

 

The PCM wasn't reflashed to my knowledge. After I posted this thread, I started thinking and did some more digging on past threads. I'm thinking my ranch hand front bumper, extra fuel tank in the bed, and M/T tires are all contributing factors to a decrease in mpg.

I'll check the brakes sticking too when I get back home, but I just had a brake inspection done in Dec and everything looked good then.

Could you explain what reflashing the PCM would do?

Thanks!
Tim

 

Well I am no expert on this subject so maybe someone else will jump in, but depending on how big of a tire change you will actually change your actual gear ratio. The comp. is programed with all of the info in it like tire size and rear end gear ratio so it can accurately calculate everything it calculates. This will also make your speed O off a few mph also, so you can check that against another vehicle for a quick test. I hope that is not only helpful but also correct!

 

Also as far as breaks go, check the E-brake they have a tendency on these trucks to get rusty and start to not completely release. At first this would probably affect mileage, but as it gets worse it will start to cause an intermittent vibration. I have had two trucks from an 04 to an 08 due this. After driving for a fair distance see if the rear wheels or backing plates are getting abnormally hot, be careful they could be real hot! The e-brake is like a mini drum break set up on the back side of the rear rotors.

 

gotcha, PCM reflash = recal speedo. I never had this done. I'll check into this to see if this could somehow affect mpg.

I use the E brake everyday, so the possibly of it getting stuck is probably higher than those who never use it. I'll do some driving and check if it gets extra hot in the rear.

Thanks for the gouge.

I'm thinking after reading many threads that the PSD just simply doesn't get the fuel economy of the Cummins or Duramax and to add to it, I have the extra weight of the 75 gal fuel tank in the bed plus the ranch hand bumper (extra weight and not aerodynamic).

If there's a fix, I'll find it. If not, I still have a bad *** truck that can pull the hell out of my 40ft fifth wheel...so either way I'm a happy camper.

Thanks again!