2000 GMC Sierra Sudden gas mileage plunge

2000 GMC SIERRA
62,000 MILES • V8 • 4WD • AUTOMATIC
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T. R. PARKER
  • MEMBER
  • 1 POST
My 2000 GMC Sierra 3/4 ton 4x4 was getting getting about 13mpg (not good to start with) when it suddenly dropped to 8mpg. Plugs, air filter and O2 sensor have all been changed out to no avail. Any ideas on other avenues to investigate? This is a farm truck that has to be used; help!
Apr 15, 2010 at 6:11 PM
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BMRFIXIT
  • ✓ASE Certified Mechanic
  • 19,053 POSTS
  • ASE Certified Mechanic
Do you have check engine light on ?
Check for trouble codes
check for a leaky injector or fuel regulator
do an injector leak and fuel system test
Apr 19, 2010 at 6:38 AM
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