Grrrr, I have dark grey smoke...
 

A few days ago I was sitting in the drive through window and thought I seen dark grey smoke coming from my tail pipe so when I got home, I let the car idle for about 30 minutes, no smoke.

Tonight I drive home, stop in front of the house and as the car idled for about 2 minutes, it was smoking out of the tail pipe. It is dark outside but the smoke looks dark grey. Grrrrrrrrr, I have about 214,500 on the dash with great compression. My guess is that I need a valve stem seal job, am I correct or should I check something else out like the turbo?

I changed the PCV about a year ago.

Valve seal, you mean? That's my guess.

I would look at the turbo first; plus it's probably the easiest to R&R..

From my experience if you're seeing oil smoke, here's how to diagnose:

1. Smokes mostly in the morning when you first start up after engine has been sitting for some time; rather big cloud that will diminish as engine runs: valve guide seals.
2. Smokes mostly after long downhill (where you're off the gas); then you get on the gas to see a cloud behind you: oil control rings.
3. Smokes pretty much same all that time: turbo seals, unless you have a N/A, then you just need a whole friggin OH.
4. All above assumes you don't have an issue with clogged pcv of course.

Ok, I'm out of town and this place has miles of down hill grades and this is what's going on.

I'm driving down a slight grade, I'd say 2%. I'm giving it just a little gas to get up to speed between lights and but the car is mostly just coasting along. I noticed over the past couple of days that it really smokes if I have S selected and the car is doing some engine braking. By the time I'm at the bottom of the hill no one is tailgating me anymore, it's smoking pretty good. No smoke at all when driving up hill or normal around town, mainly just after long down grades and especially with engine braking.

So, where are "oil control rings"?

On the pistons.

You're a dino oil guy, right? Try an Auto-Rx treatment. Worst case it's 30 bucks down the drain.

No, I use full synthetic. I also have (had) great compression numbers about 8,000 miles ago. 174 Was the lowest number and the highest was 179.

So, is dropping the oil pan the best method to deal with that?

+1 on gdog

Probably not oil control rings then.

I've been running synthetic for about 25,000 miles.

So you're burning a little oil; unless you're using more than a quart in 500 mls, I wouldn't worry about it. Of course if you're looking for an excuse to do an OH, there you go..

It's very possible to have good compression numbers, but the oil control rings still not seal. Seen it more than once..

It's not burning any more than usual. I changed it about 1,100 miles ago and it has lost about 1/4 quart. It's the smell that bothers me more than anything. And the fact that this will likely file my o2 sensors and my catty.

Piston rings can stick but it's usually from lack of maintenance. You take care of your car and change oil regularly and it's very unlikely they would be the cause.
Normally they will cause a problem when a vehicle has sat for a long time. The Upper "compression" rings can stick too causing a lack of compression.

Crazy thing, less smoke today and yesterday. I changed the o2 sensors and now I'm not seeing any smoke. I'll have to check closely tomorrow.

Ok, I finally got a video of the car smoking. It's uploading now and it will be avaible here on youtube. Please let me know what you guys think it is. Again, it doesn't smoke all the time, doesn't smoke on start up. Just ever once in a while and if I coast for a while it will smoke.

Here is was smoking while sitting on the highway while waiting for an accident to clear.

My N/A was doing a similar thing under what seems to be the same circumstances. I used a bottle of Lucas oil stabiliser which is suitable for synthetic oil, and it has not done it since. My mechanic told me it was my vale stem seals starting to go.

Lucas oil stabilizer is a high viscosity dino oil - 80 weight I believe - with tackifiers. It does reduce oil consumption by significantly increasing the viscosity of your engine oil but at the risk of oil starvation to your top end, particularly in cold temperatures.

You'd be better off installing a high quality 20W-50 oil in your engine.

They make a synthetic stabilizer and although I haven't used it myself they call it "light, slick and long-lasting". Doesn't really sound like an 80 weight but I could be wrong.

Lucas Pure Synthetic Oil Stabilizer reduces friction for more power and more MPG. It works to eliminate dry starts in new engines and provides the extra protection needed for import and domestic engines requiring newer, lighter engine oils. Lucas Pure Synthetic Oil Stabilizer was originally designed for the racing industry and is light, slick and long-lasting with a film strength that stands up to high temperatures and pressures in extreme situations.

What's the chances of this being my turbo? Most of the stuff behind there is rusty so it's scary to tear something apart just to take a peek.

I use a good quality synthetic oil, and it still blows blue smoke, the lucas stuff so far has been the only thing that has stopped it. I don't need to worry too much about cold temps here, our winters are usually about 55F