Decreased mpg

[AgsChevy]

I've got a 2000 3500 that get 12 - 13 mpg now with 89,000 miles on it and used to get 14 - 17 mpg for the first 75,000. Had a leaking intake manifold gasket and changed it and since have not gotten over 13 mpg. I had it retimed at a shop and they said it was fine. I replaced the two oxygen sensors before the catalytic converter two weeks ago and was told that possibly anti-freeze got to the sensors and ruined them. That didn't help. Any ideas?

[dannyukonxl]

 

http://www.gm-trucks.com/forums/index.php?...showtopic=32205 might be your egr valve