This week was a bit different. I set my cruise at 65mph (1,325rpm) for the entire trip. The wind was calm and not much stop-n-go this week. I avg'd 7.25 loaded and empty both ways. The truck ran smoother, I was able to stay ahead of most company trucks (JB, SNI, Werner, US EX) and made average time.

I think this is where I'm going to run the truck at for the next few months and start doing my upgrades...... first will be a 3 axle alignment to see if it makes a difference (plus who knows if it has ever been done) then I'm going to get the new mufflers, then have the overhead ran. After that, I'm going to try a few other things such as a ECM tune and a few online things I have read for the C13.

The good rule of a tumb;-If it's not broken, don't fix it! Of course i didn't mean scheduled maintenance intervals....

I know what you mean, but the mufflers have 520k on them now, the overhead should be done every year along with a 3-axle alignment. If I do a ECM upgrade, it won't be for at least a year, and the rest I am still 'iffy about.

I'm very particular, where i do alignment, and overhead. And definitely wouldn't mess with ECM unless i have to....

I have my alignment done at the local Goodyear dealer and my overhead will be done at Great Lakes Peterbilt

Just an update....I have been averaging 7.25mpg with the truck and am not very happy. I honestly thought it would do better since I run empty everywhere I go, and I keep it under 65mph.

That being said, today I did a mod I heard about with the fuel wire, and also my boost wire going to the ECM. The truck deff idles much smoother, and the throttle response is great. I don't think i will gain any MPG yet, but I will check it out on this weeks run.

Next weekend I am removing the resionator/convertor and putting in a piece of straight pipe, thus eliminating one issue. I have been told that I should gain about .3mpg with that, then going to replace the mufflers on the back with some Donaldson high flows and see how she does. If i can even gain .5mpg total I will be very happy!!!

You are getting about all you will ever see with a Cat, just how it is, the Cats are NOT fuel mileage engines,never were, just ask anybody that has one,

Also notice most big fleets didn't use Cats,even when they were available, there is a reason and fuel mileage is the biggest one.

True.....but I've never pulled 4500 lbs with it either so I wouldn't know. OMG that is light. Seems like overkill to me. I bet my little M11 would get 9 mpg on that run.

I bet it would too!!!! I went with the C13 hoping it would help out a bit, and it deff is better than a C15 would have been.

As for being light, I love it till winter comes around. Then it is a nightmare to deal with. Heck, even on a dry day I lock up the trailer tandems just rolling at 25mph and stopping. Scares the carp out of the 4 wheelers if I have to brake quick on the interstate. All that smoke tends to make them go for the median LOL

I'm not so sure, there are a few guys I run with who have 05-06 C15's in W9's and with the resionator removed and donaldson mufflers that are getting 7.5-8mpg pulling liquid tanks heavier than me.

I'm just kicking myself in the ass for getting rid of my old trusty FLD. I should have just spent the $2000 on the clutch and hit the road, but as usual, I had to make an impulse buy LOL