This is not the usual mileage question, and yes I searched. I have an 01 1500 sport offroad edition with a 5.9l. When I got it I was getting 9.2 mpg by the overhead console. I know they're not accurate.Anyway I gave it a complete tuneup, added a k&n cold air intake, and went with a hemifever tune. What I don't understand is that I get the best mileage with the 93 tune? I,m still only getting 11.5 on the overhead console. The truck runs fine and is on stock rims/tires.
Thanks for any insight that you may have.
Oh yea, I drive like a granny to get this mileage!

 

how long have you had the 93 tune on it?

 

what i wouldn't do to get 11.5 out of my 99 5.9

 

1 tank, a couple of days. Why?

 

Are you putting 93 octane in it with the 93 tune vs. 87 octane with stock tune? I wouldn't be surprised if you got some mpg increase running 93 octane even with the stock tune. And you get a little more mpg with the 93 tune, maybe it burns the fuel more efficiently. Makes sense I guess...

I pulled 14 mpg on a 6 hour hwy drive in my 98 4X4 with a 5.9 last week. I was friggin ecstatic. Don't have a console, figured it miles driven/gallons at fill up. Usually get around 12.

 

I'd be happy with 14. The truck runs great but the mpg is killing me!
Anyone know if a slow O2 could give a problem without giving a cel?

 

Have you checked the plenum? Remove and clean the TB? You have no sig information, and "complete tune up" means different things to different people. O2 Sensors usually throw a code immediately(stress usually, not always). Have you changed them?

 

Plenum is good. Yes I removed and cleaned the tb. Map sensor is new.
Tuneup = cap and rotor, plugs, wires, pcv, oil change, oil and air filters.
The truck just turned 80,000 miles and runs great.

Thanks for the responces so far!

 

Slow O2 will definitely effect fuel economy, and won't necessarily set a code. If they are still the original sensors, time for some new ones.

 

I had a bad TPS cut my mpg's in half! Didn't realize it until it got bad enough that it was affecting the TCC in overdrive. No codes were thrown either.