2001 GMC Yukon Poor Mileage

[belbers1]

Hey Guys,
I was wondering if anyone would be able to help me figure out why I am getting such bad gas mileage.
2001 GMC Yukon SLT
5.3 L V8
Spectre Cold Air Intake
Flowmaster Super 44 Exhaust
New O2 sensors
14 mpg avg.
12 city
15 hwy

Is this normal mileage that is to be expected from this vehicle? I added the cold air to get some power, and it helped the mpg a little bit. Anything I can do?
Thanks guys

[maxwedge]

You could do a full scan and look at fuel trim readings to see if the engine is running rich.

[belbers1]

Do you know where I would be able to do that cheaply? I don't want to pay $40 for a diag. fee if I don't have to.
Thanks

[maxwedge]

No, this requires a fulls can, unless a friend has one you have to have a regular shop do it.

[belbers1]

Ok. Thanks. I think I'll just leave it as-is because I plan on selling it this summer to get a diesel truck.

[belbers1]

The diesel truck plan ended up falling through. I am thinking that a major reason my gas mileage is bad is my spark plugs and wires. They are the original. Any recommendations?

[hinton08]

yeah. replace the plugs and wires with AC delco. They may be higher than aftermarket but they are well worth it. I work at a GM dealer and there IS a difference in parts brands. Check your air filter while your at it, and if dirty, replace it as well.

[JustJimBo]

sorry to say, but that is not "bad" MPG...it is just what the vehicle gets....I've owned one for about 8 years now and that is the average...14.

[hinton08]

Yep thats exactly right. They average 14 mpg. 12 in the city, 16 on the highway. Just keep your vehicle well taken care of n it will stay at 14 mpg

[belbers1]

Sorry for getting back so late guys. I ended up finding out what it was. One of my friends put in a new o2 sensor, and for some reason put some antiseize on the threads. Turns out the antiseize shorted the sensor out when it liquefied. Now, during the summer, I avg. 15.5 mpg. During the winter I get 14

[hinton08]

antisieze is actually a good idea. it keeps the O2 sensor from getting stuck and siezed up in the exhaust pipe and makes it much easier to remove if needed. You just have to know how much to put on so you dont have problems like this.