poor mileage, but no other problems on '10 PPV

[CrashTestDummy]

Our 2010 PPV seems to be running fine, but the mileage has recently just tanked. It used to run at about 16-17 in combined driving, and when I drove it on the weekends, I could frequently back it into the garage with a 18+MPG average. I'm easier on the loud pedal than she is.

But lately, the thing has been posting a low 13-mpg average. I got in it yesterday afternoon and it had a 13.3 MPG average. I was able to get it up to 13.6, but that's still not good.

The truck seems to run fine, performs well, although my wife said it did hesitate a bit when she was going to drive around someone and matted the accelerator, but after that, it ran fine. It performed well for me, too.

There is no CEL on, but I haven't checked it for codes. I plan to do that the next time I get some quality time with it. The tire pressures look good, and the tires are wearing fine.

The only work we've done is replace the vapor purge valve assembly, and the evap solenoid, but it was already posting the low mpg before I replaced it. The replacement hasn't improved that any.

Thoughts? The truck has a little over 100K miles on it now, and we have a BB tune on it that's about 2 years old.

 

[1clean08denali]

Not sure about your situation but on my chevy 2500hd it did the same thing about 110k I changed the plugs and did a fuel system cleaner and changed my air filter and that solved the problem. Truck ran great for another 130k

 

[CrashTestDummy]

Hmm, plugs are questionable. We bought the truck at 82K miles, and it ran great then. The air filter is a K&N drop-in, which I installed when we bought the truck, so hopefully that is still fine. I may think about plugs and wires.

 

[Grimes]

Hmm, plugs are questionable. We bought the truck at 82K miles, and it ran great then. The air filter is a K&N drop-in, which I installed when we bought the truck, so hopefully that is still fine. I may think about plugs and wires.

The K&N drop-in is washable, and its pretty simple to see if its fine/wash it off anyway.

If you bought it at 82 the previous owner may have sold before doing the fuel induction service, and you may have overlooked it because it is so close to 75. If you've never done that, its at least worth an inspection.

 

[ccapehartusarmyINF.(ret)]

if its got a black bear tune and yer mileage goes in the toilet all the sudden theyd be the first number id dial

yer not running e85 are you

 

[CrashTestDummy]

No e85 here. At least as far as I know. It's my wife's DD, and we always run premium. Don't the pump handles on e85 pumps have different colors? I've never actually seen one around here. We do have 10%, but not e85 locally that I know of. I guess the supplier could have dumped e85 in the storage tanks, but that would have some people angry. Verifying that's not an issue is definitely something to check, though.

The tune is 2 YEARS old, so I'd doubt something in it has changed.

The truck was in service before we received it, and it appears the Sheriff's department took pretty good care of it when they had it. It ran great when we got it, and was dang quick even before we tuned it. Plugs aren't something they would probably bother with, unless there was a real problem, one would think.

 

[CrashTestDummy]

Update: Cleaned the MAF. It looked fine, but I hosed it down anyway. The truck now reports almost a 1 MPG gain. Next up is the TB.

 

[ulakovic22]

With the mileage I would do a tune up, clean the MAF, TB, replace the air filter, plugs and wires. I'm in the same boat, when I purchased our Suburban used I was getting 16+, now I'm getting low 13's.

 

[devious1]

is everything sticking with oem wires and plugs or going with some thing aftermarket?

 

[ulakovic22]

I'm looking into FireCore wires. Not a fan of OEM. Delco plugs.