2003 Yukon Horrible Mpgs

sagent · January 22, 2009

My 2003 Yukon has been consistently getting horrible gas milage. Lately its been about 9.5 mpg around town with my wife driving it. It's the short version ( non xl) with a flex-fuel 5.3 L and 3.73 gears. The truck has about 115,000 miles and I bought it with about 95,000. I've changed all fluids to Amsoil and have lately been running Mobil 1 0w-30 in the crankcase. The truck has stabilitrac and came with the borg warner 4482 full time 4wd transfer case ( rpo code NR4 ). I would like to know if anyone else on the forum has a similar suv with this drive train configuration and what they are getting for milage in order to compare.

Other than the milage the truck runs perfect and has had all scheduled service performed, new plugs / wires / good tire pressures & no check engine light.

The only reason I think the is a problem is that my fathers 01 Yukon Denali has been getting about 3 mpgs better throught its life. The only thing I can think of is maybe the fuel composition sensor is malfunctioning causing it to burn gasoline as it would burn E85.

jrrod2004 · January 22, 2009

My 2003 Yukon has been consistently getting horrible gas milage. Lately its been about 9.5 mpg around town with my wife driving it. It's the short version ( non xl) with a flex-fuel 5.3 L and 3.73 gears. The truck has about 115,000 miles and I bought it with about 95,000. I've changed all fluids to Amsoil and have lately been running Mobil 1 0w-30 in the crankcase. The truck has stabilitrac and came with the borg warner 4482 full time 4wd transfer case ( rpo code NR4 ). I would like to know if anyone else on the forum has a similar suv with this drive train configuration and what they are getting for milage in order to compare.

Other than the milage the truck runs perfect and has had all scheduled service performed, new plugs / wires / good tire pressures & no check engine light.

The only reason I think the is a problem is that my fathers 01 Yukon Denali has been getting about 3 mpgs better throught its life. The only thing I can think of is maybe the fuel composition sensor is malfunctioning causing it to burn gasoline as it would burn E85.

I would change the O2 sensors, then I would seafoam it (if you haven't already done that), change the oil and then disconnect the battery to remove the old adaptive settings. Then take it out for a drive (anywhere from 25-150 miles) and you should start to see its mileage improve. I would check to make sure it is not running rich as this can be wasteful... others will chime in as well.

Draenor · January 22, 2009

My 2003 Yukon has been consistently getting horrible gas milage. Lately its been about 9.5 mpg around town with my wife driving it. It's the short version ( non xl) with a flex-fuel 5.3 L and 3.73 gears. The truck has about 115,000 miles and I bought it with about 95,000. I've changed all fluids to Amsoil and have lately been running Mobil 1 0w-30 in the crankcase. The truck has stabilitrac and came with the borg warner 4482 full time 4wd transfer case ( rpo code NR4 ). I would like to know if anyone else on the forum has a similar suv with this drive train configuration and what they are getting for milage in order to compare.

Other than the milage the truck runs perfect and has had all scheduled service performed, new plugs / wires / good tire pressures & no check engine light.

The only reason I think the is a problem is that my fathers 01 Yukon Denali has been getting about 3 mpgs better throught its life. The only thing I can think of is maybe the fuel composition sensor is malfunctioning causing it to burn gasoline as it would burn E85.

I would change the O2 sensors, then I would seafoam it (if you haven't already done that), change the oil and then disconnect the battery to remove the old adaptive settings. Then take it out for a drive (anywhere from 25-150 miles) and you should start to see its mileage improve. I would check to make sure it is not running rich as this can be wasteful... others will chime in as well.

+1 but minus the 02 sensors.(just for the moment as they are pricey to replace) IF you cant get a way to use or borrow a wideband, pull the plugs and see if there is an abundance of fuel on them.

C & A s Dad · January 23, 2009

Seafoam it as said. Run a couple of tanks with some Chevron Techron and if you have not looked at the plugs and wires, I would replace them. I am sure you have already done the obvious, air filter, tire PSI, etc. etc.

My 02 Yuk XL (4.10 gear) is a 2 WD so maybe not a fair comparison but I averaging almost 18 right now with mixed rural and highway driving. This is real calculation, not the avg from the DIC.

DBVille · January 23, 2009

Don't rely on the computer for mileage - check it the old fashioned way - write it down and divide it out. After checking all the normal suspects - plugs, air pressure, O2 sensors, what everyone else mentioned, there is one more thing.

The driver. Don't laugh. My wife gets worse fuel mileage than I, by at least 10%, in every vehicle we have - Suburban, Subaru, whatever. She accelerates faster, and brakes later than I do when on the street. We both run about the same speeds, but the acceleration kills mileage.

Edit: Yes, that is lousy mileage - our 2500 Suburban gets 10 mpg+ under almost all conditions, and it probably weighs close to 1,000 lbs more. Our 2000 Suburban got at least 12, and up to 16 mpg.

Porter_ · January 23, 2009

Don't rely on the computer for mileage - check it the old fashioned way - write it down and divide it out. After checking all the normal suspects - plugs, air pressure, O2 sensors, what everyone else mentioned, there is one more thing.

that really is the old fashion way . instead of doing long division while you're sitting in front of the pump, save yourself some time and use your cell phone calculator. don't even need a pen and paper