Baffling MPG in the 450 with CEL light on

[bkgiii]

I’ll be as brief as possible, but this MPG thing has me baffled: Three weeks ago, CEL indicated EGR issues, so VSV, EGR, O2s, tubes…all that stuff…replaced. MPG at that time (following repairs) was about 13 on the highway. A friend has had the 450 this week moving from FL to MS, pulling a 12’ utility trailer. On the way TO FL, w/trailer empty, he reported 13.5-14 MPG. Two days ago, while in FL, he said the CEL came on again. He just called me today, almost back to MS, and WITH the trailer fully loaded and stuff in the back, he has gotten 15.5 MPG over two tanks of gas. WITH the CEL light on………

What’s up with that?

 

[concretejungle]

perhaps his math is off? I mean seriously, when you are precise as .5 miles/gallon things have to be pretty precise when calculating.

 

[alaskacruiser]

bkgiii- do you know for sure that the CEL is a P0401 (related to your previous problem)? It may not be. Also, not all CEL problems cause a loss in fuel economy.

 

[bkgiii]

No, I don't. It just seemed off that the previous P0401 issues, once resolved (I think) resulted in NO CEL and lesser MPG than what he's now seeing WITH a CEL on. I've not gotten the vehicle back yet, and haven't pulled the codes. BUT, if he's saying he's getting 15 (or thereabouts) WITH a fully loaded trailer, maybe a CEL is a good thing?

C-Jungle, I agree....I question the precision to .5 But, a full 2 MPG more?