Hometheaterman, I'm getting about the same numbers as you coming out of winter, and I don't run quite as many mods as you. I also run 89 octane fuel because its the cheapest out here in SD (ethanol). What are your temps/weather conditions when you're getting those #s? When I got these numbers, it was about 30-40 degrees on average, and we did have a little snow at times (I think I engaged 4x4 once so I could go in the ditch to help out some women who slid off the interstate).

Not to jack the thread, but I also had a question for you, since you mentioned your Auburn... why are you not supposed to use synthetic in it?

 

How did you figure your mpg? I wonder if you had been going 60 if it would have been 20!

 

I'd say temps range anywhere from 20-60 degress maybe slightly more and I seem to be getting about the same. I get in the 10's if I drive it around mostly town and don't do it easily but as long as I don't drive it like it's a race car I can do better than that. Maybe it's the winter gas idk. I get in the 10's or 11's too if I run cheap gas. I seem to get the best gas milage from BP gas.


As for the Auburn with the synthetic I've just read not to run synthetic in a rear end that has a lsd in it unless they specifically say to. I have a spare 4 quarts of Royal Purple gear oil I was going to put in there then read that. I will see if I can find the link to the main one I read. It's over on DTO. It just seems like from research that you aren't supposed to run synthetic in rear ends with LSD's unless they specifically say to. I guess I will save the RP for the front diff now.Can't hurt to have some spare. I buy their oil by the case usually so I have a case or two of RP oil in my garage too. I run it in all 4 of our cars.

 

http://dodgetrucks.org/forums/viewtopic.php?t=74280


There is the link. It says synthetic with the Auburn will cause it to chatter and damge the unit.

 

if i had been going 60-65, i probably could have got 19-20 mpg, but i don't know... 60mph... too slow for me. i normally do 80-85 and that feels like a good speed to me. hell i do 60 backing out of my drive. lol.

 

If you can hear the tires hum: your exhaust isnt loud enough lol

 

Oh trust me my exhaust is plenty loud enough. I can hear both of them.

 

Damn something must be seriously wrong with my truck then. I was getting about 9.8 MPG no load, and after I installed my CAI I'm at 11.3. I know I need new tires and I just did a tune up since it just reached 90k but what the hell else could be wrong? It drives and runs great.

 

veilside3kgt, you've done the obvious things, like check the tire alignment, balance, and rotation, I'm assuming? What kind of "old" tires are you running right now?

I was running 9-10 mpg during the winter in town with CAI, high flow cat, Flowmaster 44, and 3" pipe. That "winter blend" gas, a lead foot like mine, and cold temps != good gas mileage. I was even plugging in my block heater at night before I would go to work the next morning...

EDIT: I'm starting to think maybe these Hercules A/T tires that came with the truck are partly to blame as well.

 

Oh I forgot to mention I have dual 2.25" pipes I don't know if that would matter. I was told if I want to keep low end to go with 2.25" pipe if it's for duals so I did.

I also have had my tires balanced as I had them balanced 1k miles or so ago. Maybe 2k but I'd say closer to 1. I had them balanced and not long before that I'd say about 2k miles ago ball joints done so an alignment. I've checked the tire pressure and bumped them up slightly from 35psi I was running to 40psi. I think thats what I set it at. It didn't seem to matter.

I also have a built APS transmission and quite a few things like that but they didn't seem to change the gas milage from before I had them replaced.