Mine is a detroit, but the mpg dropped on it too. I was told that they may have got the valves a little tight. This makes me wonder if there would be a benefit to requesting that they be set to the maximum recommended "looseness". You would probably need to have the overhead ran more often, but if it effects the mpg that much, it might be worth it.

 

How long does this loss of MPG last? My second truck is getting bad fuel mileage. I bought it with 316,000 miles on it and had the overhead done right away.

The truck has about 345,000 on it now I think and it's only around 6mpg. About 6.5 deadhead while the other truck is more like 7.7 mpg.

I took it to the dealer and the CAC had a hole in it and also the EGR Valve was replaced but it's back on the road now and not too much better.

 

When I took my truck into KW for its initial overhead, I lost mpg. For the second, I went to Cummins. They said I shouldn't have lost any mileage and that it was probably overtightened the first time. After they performed the job, there was no change. I was back at Cummins not too long ago for some other work and was going to have them run it again. It had been over 100,000 since the last. They asked if it was running worse. I said no but manufacturer's recommendation. Their response was unless I'm noticing that it's running rougher, it's not necessary...but it wasn't going to hurt anything. KW said run it as often as possible :roll: :lol: Well, maybe not, but certainly as often as they could justify.

 

Run it.

Don't give them an excuse to not honor a warranty claim because you didn't run it as they recomended, they will look for any excuse to void a claim.

 

What he said

 

Ain't that the truth. :lol:

 

How much does an overhead cost? (just curious)

 

Last one ran me about $250 from what I recall.

 

I was out of warranty by then. During the warranty period, everything goes by the book.