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Gas mileage is still down

Tiny
GYAKUBIK
  • MEMBER
  • 2008 GMC SIERRA
  • 108,000 MILES
I have changed the spark plugs and cleaned the throttle body. The gas mileage is still down about 3 miles per gallon. Should I change the oxygen sensors and why. It has a 5.3 L in it
Saturday, February 25th, 2012 AT 1:54 AM

6 Replies

Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,004 POSTS
IS YOUR CHECK ENGINE LIGHT ON?

THE MEDIC
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Saturday, February 25th, 2012 AT 2:38 AM
Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,004 POSTS
DOES YOUR RIG SHOW ANY OTHER ABNORMAL SYMPTOMS?

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Saturday, February 25th, 2012 AT 2:40 AM
Tiny
GYAKUBIK
  • MEMBER
  • 3 POSTS
No, The truck is running fine. It's just gas mileage is down. I also keep tire pressure up to about 40 - 42
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Saturday, February 25th, 2012 AT 3:09 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,700 POSTS
Not related to the MPG, but with air pressure that high, you are going to wear the centers out of the tires.

As far as the MPG, make sure the air filter is clean, there are no vacuum leaks.
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Saturday, February 25th, 2012 AT 3:16 AM
Tiny
GYAKUBIK
  • MEMBER
  • 3 POSTS
KN filter and has also been cleaned. Not sure on checking for vacuum leaks. How can I tell if there is a leak
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Saturday, February 25th, 2012 AT 3:40 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,700 POSTS
For directions, go to our homepage under the DIY section.
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Saturday, February 25th, 2012 AT 4:14 AM

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