MPG droped 50-70%! Any ideas?

[7river]

Currently on a road trip with the bus.
I just put a rebuilt E4OD in her.
Just put on all new new rubber. Michelin LTX M/S 245/75/16

Running on veggie oil. Always got 13-16 with the oil or diesel
Changed fuel filter.
No smoke noticeable
Hear ping/tap when accelerating in O/D

Got 5 MPG first 800 miles. Droped a bunch of weight and adjusted the tire pressure from 55 front/70 rear to 65 front/75 rear
MPG went up to 8-9MPG

I started off with 200 gal of oil so we were pretty heavy.
Now we have about 100 gals plus the 35 gal diesel and gear. This weight we were getting 13 MPG in the past.
Any ideas?

 

[smolkin]

Maybe you have an injector sticking open or dribbling? You could try the ATF-in-the-fuel-filter trick, fill with ATF, crank for 3-5 secs and let sit overnight. If you're not already using an additive I highly recommend it. I always use Power Service DieselKleen at about 1.5X the recommended dose, helps with starts and gunk buildup. (works with wvo and B100, or anything you burn)

 

[Agnem]

Based on the fact that your running a cocktail, I'd recommend dropping back to streight diesel for a while, get your timing checked, and have your injectors pop tested. Wouldn't hurt to see if you have any cokeing in your precups. You can check for this with the injectors out.

 

[cowboytueller]

another idea to check for is a small fuel leak somewhere. You maybe losin fuel instead of mileage.