mileage drop after injector replacement

[chessy56]

At 176K miles, I had all 8 injectors replaced. Prior to that time, I could expect a good 21 mpg on long highway trips, at ~64 mph (about 1900 on the tach), and no head wind. With a bit of a tail wind, I could squeeze out a tad over 22 mpg.

Since the injector replacement, I'd estimate my mileage to be closer to 20, maybe 21 with a tail wind. Is this normal? I would have thought my fuel economy would improve with the new injectors. The Chevy dealership used OEM replacements (Bosch, I think). Any thoughts?

FYI: 2001 Dmax, K2500HD, LB7 currently with 213K miles, stock fuel filter only, K&N air filter. I typically run a little Lucas fuel treatment in the diesel.

Any comments on the drop in mileage?

Thanks-
"Chessy"

[DickWells]

lost some fuel mileage on mine, after the injector replacement in 07, with 86K miles on the clock. A little over a mpg, towing. From ~12.3 pre change, to ~ 11 + a wee bit, on the average, after. Just changed again in June, with 121 K miles, and I think the mileage came back up a little. I've heard, many times, that the changing of injectors on the LB7 quite often upsets the mileage a bit. I'm not complaining about the mileage, but sure would like to get your kind of longevity out of the injectors.

[Kennedy]

I think a lot of this can be from the crap between the line nut and line that gets ground up during R&R. No matter how well you try to clean them there is still junk that gets ground up during install. For this reason we use new lines most of the time.

[willydmax]

Our experience has been just the opposite, but I replaced the high pressure lines like Kennedy said. Dad is extremely happy with the mileage after the injector replacement. He's getting 19 mpg empty without trying very hard. I think with the new injectors and high pressure lines we are giving the "Kennedy ECM tune" the best chance at good mileage.