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poor mileage deisel

cut-rite

LawnSite Member
Location
mid coast,Maine
I have a 97 gmc 1 ton dually 4 spd automatic with the 6.5 turbo and 4.10 gears . It has 45000 miles and a 2-3 yard dump body,I am only getting about 9.5 miles to the gallon (highway 25%load before plowing season) I have changed the filters and checked the obvious. Any suguestions? What shoud I be getting? thanks, brad
 

TLS

LawnSite Fanatic
What size tires are you running? This seems low, however the bigger the tire, the less miles traveled and thus less mpg.

 

John DiMartino

LawnSite Silver Member
Location
Walden,NY
Do you have low power?hwta kind of mileage did it used to get?that is a heavy truck and i dont think its all that bad if your foot's in it a lot.My Dad just sold his 94 6.5 turbo ,it was in a shortbox 2wd 94'and had 3.42's.Its best mileage was 15 on the highway,a 350 could get better#'s.
 

plowking35

LawnSite Bronze Member
Location
S.E. CT
I have that same truck, and I get around 12-14 mpg depending on the load, and I to have about 45K on it.
Go to http://www.62-65-dieselpage.com, they are a gm exclusive web site, and someone will know that answer.
Dino
 
OP
C

cut-rite

LawnSite Member
Location
mid coast,Maine
more info- tire size stock 225-75-16 -small for 1 ton .I have only had this truck for 10,000 miles ,mileage has gotten consistently worse from about 12.5 down to present9.5 (same load and conditions). thanks,brad
 

plowking35

LawnSite Bronze Member
Location
S.E. CT
we changed to p235/85/16
It lowers rpms at highway speeds.
Dino
 
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