Towing mileage?

[84 Convert]

I have been getting worse mileage lately. It has gone from ~14 down to 10-12 while towing a fairly heavy enclosed trailer ( last time across the scales was just over 12K GCVW). Thing is, I'm not sure if this is ULSD related or just equipment wearing out. I have no idea how many miles are on the pump/injectors. I do know that after using Fuel Therapy additive the truck began to run MUCH better, but my mileage has not returned. I also changed the fuel filter. The old one definitely had water in it.

So, what does experience say? Bad injection parts possibly? Blasted new fuel? Give up cause that's all you're gonna get?

I'm currently running over 100mi per day, so this is costing me faster than usual. BTW this is the GMC K2500 in my sig.

Thanks,

Gregg

[More Power]

I have been getting worse mileage lately. It has gone from ~14 down to 10-12 while towing a fairly heavy enclosed trailer

ULSD by itself won't cause this. How much data do you have to support the 14 and 10-12?

Jim

[84 Convert]

I have been noticeing this change at first because it seemed I was getting fewer miles out of a tank of fuel. I then checked the mileage over several tanks to confirm my suspicions. My typical towing speed is <65.

I tried leaving the HPCA on and it looks as though I am getting more mileage that way. I am hoping to change my timing chain tomorrow, but that depends on how fast I can do the clutch.(it doesn't disengage fully to shift gears anymore, I suspect the pressure plate)

In short, I think my timing may be getting more retarded due to the timing chain stretching, thus causing worse mileage. We shall see. I may try some new injectors as well.

Gregg