2001 GMC Sierra Poor fuel mileage

Tiny
WATERGUYSID
  • MEMBER
  • 2001 GMC SIERRA
  • V8
  • 4WD
  • AUTOMATIC
  • 59,000 MILES
I have a 1500HD w/ 6.0L. What would cause my mileage to drop to 8.5-9 mpg from 10.5-11? I changed the plugs, and went to synthetic oil, nothing seems to help.
Wednesday, August 6th, 2008 AT 5:29 PM

1 Reply

Tiny
BLACKOP555
  • MECHANIC
  • 10,371 POSTS
You can change the air filter, and check to see if the tires are inflated properly, also make sure the brakes arent dragging.

I woudl suspect a issue with the o2 sensor, due to its not that much of a decrease.
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Wednesday, August 6th, 2008 AT 10:12 PM

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