I have an older, 1991, minitruck (japanese). I took it ot the shop to have some work done and they also did an oil change. They put in a synthetic blend, and it started smoking afterwards. I am aware of what synthetic oil can do to older rings so I switched the oil to 10w30 and added some "ring sealer" additive. When I did the oil change, the new oil was BLACK! I did not remove the filter as it was brand new, but likely still held some of the synthetic oil. When I start her up now, she smokes bad. More so that with just the synthetic. However, after about 10 minutes, no smoke.

So here are my questions. Should I drain the oil and then replace the filter? Just burn off the synthetic and add new oil as needed. Does the smoking cause any engine damage or just "spray for bugs."

Thanks!

Sounds like you may have blown your head gasket. Was there any gasoline in the oil?

It didn't smell like gas at all. The exhaust definately smells of burnt oil, not coolant. Smoke is blue, not white.

Another idea: may have overfilled the oil causing it to smoke.

I perfromed an oil change after he did it, and the oil level is correct. How does this theory sound...

Engine hot= seals swell and no oil leakage.

Engine cold= seals shrink, oil leaks, thus smoking at start up and eventually burning off.

Here's a quote from an engine guru on another site I frequent regarding oil in general. This quote was pulled from a much longer post he made, most of the post has nothing to do with your situation, but I thought this might provide a bit of insight to what you're experiencing.

"Note regarding switching from mineral to synthetic: There's a lot of feedback that making this switch causes engines to develop leaks. This can be the case, but it's important to understand why. Synthetic oil is more solvent than mineral oil, meaning that it can clean and remove deposits left my mineral oils - and expose worn or damaged oil seals. If your engine currently uses more than about 1 quart every 1,000 miles, you may experience leaks by switching. Note that this solvency is a good thing; this is exactly what keeps an engine far cleaner when running synthetic."

So maybe switchback to synthetic with an additive? I would prefer to have damaged seals, using mineral oil, with no smoke. But it looks like it might be two late for that. It's as if my engine got a "cleaning" from the sythetic, that has resulted in this problem.

Yep, and unfortunately the way I see it those deposits ain't gonna come back any time soon to seal everything back up the way it was. This is the reason I'd never switch a high mileage motor over to synthetic oil. I know it wasn't your decision, but it would seem like the cat is out of the bag now.

I have a 1994 Land Cruiser, switched to synthetic oil at about 175K miles. The first change was to Mobil 1 (10W-30) everything was great. I let the Mobil one go for around 12,000 miles before changing oil and filter. Next change was to Mobil 1 (20W-50) and the oil pressure shot up really high, I only ran that for around 7K miles and switched back to 10W-30. I run it now around 12K miles between changes. The old girl just turned over 214K miles yesterday and still running strong. I expect to get another 100K miles out of her...

How long did you run the syn? Was the old oil really old/dark? Sounds to me like the syn picked up a little of the old oil in the crankcase, which accounts for the blackness. If the rings have a little wear on them, the syn 'slipped' past the rings while it sat and there's your smoke.

Not long at all maybe 2-3 days, and a total if 15 miles of driving. I wish I would have tken a picture of it, but it was dark.

Will synthetic burn and be as smokey as regualar oil? Now that the syn has been run through it, would it just be better to keep running synthetic?

first of all if you change oil you change the filter every time. If not you might as well just leave the old stuff becuase your new oil is contaminated now

mixing different oils is not a good idea

Sounds like worn valve guides if it only smokes after you start it. gotta be oil leaking down to the pistons from the head. I am not sure what type of seal they have on the valve stem.

x2

X3

Get some moreys or lucas oil stabilizer, try about a half a bottle with your oil now sounds like you may have some burned valve guides. This will lube dried valve guides. Maybe stop the smoking, only about a 10 dollar fix if it does. My scout did this when i tried to switch to synthetic oil.

If it starts smoking the second you crank it more than likely its bad valve guide seals...I bent wrenches in the automotive world for a few years and I seen this several times. If this is what the problem is it will clear up ans soon as the engine warms up all the way. There may have been enough crud built up around those seals with the regular motor oil to keep the oil at bay, but like was previously stated synthetic will dissolve all the crud loose because of its properties. When these seals become worn as the oil is being pumped across and through the valve train the oil will run down the valve stem especially into the intake valves because there is always vacuum present. Most shops can change the seals very easily. Also check to make sure that the drain back holes in the heads aren't clogged. Back in the 70's and 80's when the oils had a lot a paraffin in them the crud, a mixture of carbon a paraffin, would stop the holes up in the heads that allowed the oil to return to the oil pan and the head would fill up with oil and submerge the valve seals in oil. They weren't designed to do that and the oil would leak down into the chamber area of the head and on top of the pistons causing massive amounts of smoke at start up.....I fixed a lot of vehicles back in the day with a clothes hanger, and a rifle barrel brush using spray carburetor cleaner and then changing the oil after cleaning with the results being no more smoke. Sometimes I would see engines that were so bad that the spark plugs were fowled out and I would have to change those as well.

try seafoam