Can a transmission that appears to be working normal be causing a 7-8 mpg loss?

i have had injectors replaced twice and it still has not helped. the CAC was also checked for leaks but none were found.

There is smoke but i cant see it unless its at night and there is someone behind me.

If you need more info please let me know.
thanks

 

When did this loss start? Winter fuel will cause some drop in mpg. Whats the specs and mods on your truck?

 

The loss has been there since i owned the truck. Bought 2yrs ago used w/125k miles. I called the previous owner and he said he had no problems. He traded up to a dually.

Edge Evolution
5" exhaust from turbo back
K&N Cold air intake
Thats about it.
And in December i did put a new set of tires on 285/70 R17

 

So what is your mileage and are you hand calculating it? A dirty air filter can cause it(I would ditch the k&n anyway) Dirty fuel filter, Poor fuel pressure. Driving style can greatly effect it. If im in the city I only see about 13mpg.

 

Uh.....what's your mileage???

 

Fuel mileage in town is 6-8
Hwy is 12.5

all hand calculated.

The meter showed 16 for the hwy.

i have a new air filter and i will be changing it. as my siren speaker rubbed agains it and mashed it in. BUT will a air filter really gain 7-8mpg?

What air intake/filter would you recommend.

I have changed the fuel filter and the shop that changed my fuel injectors said fuel pressure is good.

Had a new fass lift pump installed a few months back to.

 

the answer to your question in my opinion is yes, check other simple things people are mentioning but If your transmission is getting ready to go or needs work there can be a large change in MPG because you are loosing alot of power through the trans

 

I recommend a dry type filter on any diesel. I run an afe pro guard filter with a outer wear on it to help it. I would be sure of your fuel pressure. It might of been good a few months ago but that can change.