09 suburban 2500 fuel mileage

[gmcjohnny67]

Ok I looked to see where 09 suburban would fit I couldn't fit a spot so I picked here I took my 01 suburban off the road the reduced engine mode problem was going to kill me well the wife said we are getting you another truck well it is an 09 suburban 2500 with 64300 miles I want to say it was a government vehicle because I see where the extra lights were mounted well to the question what should a 09 suburban 2500 with 6.0l gas get in fuel milage so far the best I got was 9 mpg I'm guessing something must be wrong 

[CamGTP]

Low teens in something like that when doing 65-70mph.

 

Depending on tire size, gearing and overall weight can determine the outcome a little bit.

 

Doing a tune up wouldn't hurt. Clean the MAF and throttle body. Inspect and change the spark plugs because they are 11 years old by now. Check over the vehicle with a live data scan tool to make sure things are working right. If it was me I'd be looking at o2 sensor operation and fuel trims to see if anything is off there.

[gmcjohnny67]

Thank you I didnt think of u2 sensors my 01 around town got 10-12 but this 09 gets 8-9 I usually do complete tune ups when I get something new I got stuck working an honey do's on the weekend I'll try changing spark plugs sunday should I use the same plug or is there something better

An 09 has

6.0l gas 350hp

6L80e trans

Rear end 3:23 ratio

01 burb has

6.0l gas 275hp

4L80e trans

Rear end

3:73 ratio

 

[CamGTP]

I would only run the factory AC Delco plugs in it. I don't remember the part number off hand, I think it was 41-110 or something close to that.

 

I knew it had the 6 speed auto in that year but wasn't sure on gearing. I'd even double check your glove box RPO code because 3.23 kinda seems odd for that truck. I would have figured 3.42's or 3.73's in a Suburban like that.

 

GU5 is 3.23's

GU6 is 3.42's

GT4 is 3.73's and GT5 is 4.10's.