It isn't a diesel but any suggestions?

[EdHale]

My nephew has the following truck:

2007
Chevrolet
Silverado
Gas
90,000 miles
2GCEK13M771638846

Several thousand miles ago it started burning oil. He just got out of the Air Force and most of it's usage has been up and down the highway back and forth to his home. Each trip would be 1,500 miles round trip. It would burn 1-1.5 quarts of oil on each trip. It runs good, doesn't miss, isn't leaking on the ground. He just got here a few days ago for Christmas and I noticed the exhaust appears to look more like my diesel than a gas engine should. I'm not saying it is black, but it definitely isn't light tan.

Does anyone have any ideas what could be wrong and if it might be considered emissions related. We don't have emissions testing in Alabama so he doesn't know if it would fail or not. I know some of the emissions warranties are up to 100,000 miles so that is of key interest in addition to what might be the problem.

Thanks for any help.

[convert2diesel]

Sounds to me like a PCV issue. The LS engines are usually really good and rarely burn a quart between oil changes.

Bill

[EdHale]

I didn't think of that, but that is a cheap fix and I'm sure it has never been changed. He just said he would change it this evening after work.

[DieselDavy]

Let us know what fixes it Ed.

[EdHale]

Will do. He just started his new job after separation from the Air Force this past Monday, so working on an oil consumption problem hasn't been high on his priority list.

I will report what he does and the results soon. I'm sure the PCV valve will be tried this weekend.

[TrenchFoot]

I'm gonna guess the truck has a 5.3L? There was an issue with that engine burning oil like mad. Something about the system that shuts down cylinders. There was an extended warranty period for the 07s for that issue. My neighbor had one in his Avalanche that the dealer had to put new pistons and rings in. I think he may have gotten a fresh set of heads out if the deal too? He'll want to get it in soon, I think the extended warranty runs out at 100k.

[crashz]

My 04 1/2 ton with 5.3L was great on oil to about 150K miles, then started burning a little. It also would depend on brand and synthetic or conventional. Good synthetic would last longer. Another thing to look for a is loose oil filter. Both the 5.3 and my 6.0 leak oil occasionally and each time its always a loose oil filter.

GM had oil burning and piston slap issues on the early 4.8, 5.3 and 6.0 LS engines also. They even stated that 1 quart per 1000 miles was acceptable consumption. My 04 was a slapper. I traded at 178,000 miles and she was still running great.

So if its no worse than 1 qrt per 1000 miles, I'd tell him to keep an eye on the oil level at each fill-up and enjoy the truck.

[EdHale]

He drives the truck 50 miles a day for his commute to work. It is 25 miles each way and 98% is highway speed. The engine does not leak, it just burns a bit of oil. He does watch it frequently and just adds a quart when needed.

Oh well.

[TrenchFoot]

Search around for the term AFM and oil consumption. The active fuel management system GM implemented deactivates 4 cylinders when cruising unloaded. Your son's highway driving is exactly what kicks the AFM in. But something about the way they implemented it causes excessive oil burn in the deactivated cylinders.

If it's still under warranty GM tends to replace pistons and rings as a starting point. If it's out of warranty, buy oil by the case. I've heard from friends that 1 qt per 1000 miles is common if you cruise at highway.