Crap fuel mileage

[Short Bus]

Im not one to usually bitch about fuel mileage but this is rediculus. 11.9 mpg unloaded over 675 miles this weekend. I had suspected it was fairly low but due to so much city and back road driving it isn't really a good way to figure fuel mileage. Just to put this in perspective, my super duty running a large single charger, huge injectors and lowered compression will do that mpg with mixed city hwy driving.


The truck is slightly lifted due to the rsk, I suppose it's 3-4" higher than stock. It has 373 gears with 305/70/16 bfg at tires. Egt's are roughly 10x the speed of the truck, so at 75 it's sitting somewhere around 750* which in my experience is fairly normal for that speed. The truck drives nice and smooth with no smoke, so I really cant understand why my mpg is in the damn basement. I expect this truck should be getting 16-18 mpg if not more cruising at 70-75 mpg. Any suggestions? The only thing I'm thinking is a tuning change to see if that helps.


Edit- running stage 2s and a stock charger

 

[~NASTYSTROKER96~]

yea stage 2s will do that with a stock charger, need a bigger turbo and maybe better tuning

 

[Short Bus]

yea stage 2s will do that with a stock charger, need a bigger turbo and maybe better tuning

How will a larger, laggier charger help an already smoke free setup?

My turbo is in good condition, up pipes are tight, no exhaust manifold leaks and based off of the fairly low egts it's probably safe to say that there's no boost leaks either. Something's definitely gotta be off track but I don't know what, 12 mpg just plain sucks.

 

[Gootee]

Fuel leaks anywhere? Odometer calibrated correctly? Brakes hung up slightly ( e brakes like to hang up on these I've seen) maybe the ebpv? just a few thoughts.

 

[Mike's Diesel Performance]

yea stage 2s will do that with a stock charger, need a bigger turbo and maybe better tuning

Your an idiot, that is the most flawed advise ever!


Luke I would be looking at the easy fixes first like brakes hung up, wheel bearings and the such. It is suprising how much a slight brake grab can kill fuel mileage. I would also check tuning, icp/ipr values and possibly even swap the IDM out. I recently had a truck come in for weird random symtoms and ****ty mileage, just happened to swap out the IDM for the hell of it since I couldn't get it to do if for me and the customer came back a week later saying his problems all went away and the mileage is up 3-4 mpgs. All I can guess is that the IDM was for some reason putting out a lower voltage and it wasnt firing the injectors properly. Good luck bud.

 

[Short Bus]

I checked the brakes last night when I rotated tires and they were ok. I never thought of the idm, I will swap that later today. Also trying some different tunes to see if that helps. Oh ands yes the odometer is correct.

 

[PsRumors]

Has it always had poor fuel mileage or is this new? Any changes that could have cause the fuel mileage?

I was chasing 2 - 3 mpg after doing basiclly everything in my sig over last winter. Turned out to be the BFGs. I went from getting 17 - 19 to 13 - 15. After getting rid of the BFG T/As I am back solidly in the 17s.

 

[zilla68]

Has it always had poor fuel mileage or is this new? Any changes that could have cause the fuel mileage?

I was chasing 2 - 3 mpg after doing basiclly everything in my sig over last winter. Turned out to be the BFGs. I went from getting 17 - 19 to 13 - 15. After getting rid of the BFG T/As I am back solidly in the 17s.

what tires did you go with?

 

[PsRumors]

Firestone Destinations...they seem to work as well as the BFGs.

Both were the same size 285s.

 

[zilla68]

how was the wear and did you get good longevity out of them? my bfg's seem to wear fast all the way around.

 

[Tom S]

My vote on this is that it is tuning related with winter fuel helping out the cause as well.

 

[PsRumors]

how was the wear and did you get good longevity out of them? my bfg's seem to wear fast all the way around.

I've only had the Destinations for 2k miles...the BFGs I think had 3k miles on 'em

 

[TyCorr]

Bfg has meant better effin get new tires for the last ten years anyway. Im thinking something like a nitto terra grappler or procomp extreme at would be good for highway mileage.

I am with Mike and think the stg IIs and stock turbo arent the culprit. If the brakes are dragging wouldnt that create a load and cause his egts to be higher? 750 is pretty cool! My superduty with stock sticks and stock charger would run about 800 at 65, the 38r reduced the temps by 100 and some.change.

 

[TyCorr]

One more thing, OP,hows your tire pressure? Wheel bearings? locking hub sticking?

 

[woodduck97]

Your an idiot, that is the most flawed advise ever!


Luke I would be looking at the easy fixes first like brakes hung up, wheel bearings and the such. It is suprising how much a slight brake grab can kill fuel mileage. I would also check tuning, icp/ipr values and possibly even swap the IDM out. I recently had a truck come in for weird random symtoms and ****ty mileage, just happened to swap out the IDM for the hell of it since I couldn't get it to do if for me and the customer came back a week later saying his problems all went away and the mileage is up 3-4 mpgs. All I can guess is that the IDM was for some reason putting out a lower voltage and it wasnt firing the injectors properly. Good luck bud.

Damn Mike you just may have found a fix to my buddies 2000 SD. He has had a loss in MPG over the past year or so. Even when he switched to stage ones he mpg strickly highway is only around 13 to 14.

 

[TyCorr]

Is this something I should look into? The idm? Im pretty sure its my stocker. Im getting 15 in the winter, but im lifted and on 37s with stock 3.73 r&p? In the summer, empty, im closed to twenty but(this is a huge but) I drive it for economy. I watch the lie-o and now the cts and accelerate until the instantaneous mpgs drop and then I back out slightly. Its just not much fun! I drive in my race tune, fwiw.

 

[Short Bus]

One more thing, OP,hows your tire pressure? Wheel bearings? locking hub sticking?

Pressure is 45psi, nothing is hung up. I got some php tunes on the truck last night so I will see if that helps, if not I will swap idm.

 

[superduty4x4]

I'm kind of in the same boat... I lost 2-3 mpg consistently when I put my stage 1's in and now with winter fuel and the occasional idling to warm up my MPG is crap... 12mpg average. Intake, exhaust, Tyrant Tunes, Hypermax Stage 1's, SD IDM, mod 17° HPOP, 35/12.5/16.5 tires. I was running 33/12.50/16.5's but the bigger tires didn't affect mileage at all.

 

[zilla68]

so if I go to stage 1's will mine increase to 12, lol? I was getting 10-11 religiously until I switched to matt's tunes, and jumped to 15 on the highway. hell I'd even consider swapping out my d60 and go to 2wd, love the truck, but mileage sucks

 

[OBS>SD]

Your an idiot, that is the most flawed advise ever!

Yea that's probaly gonna help you get business by Being rude. I know who not to buy from.