Greetings. I have a 97 850 NA with about 180k on the clock. Last week I noticed white smoke spewing out of the tail pipe during the morning commute. Ever since I haven't noticed any smoke.
I had a compression test done on the engine and it came out as:
CYLINDER 1 195
CYLINDER 2 130 (195 WHEN WET)
CYLINDER 3 190
CYLINDER 4 195
CYLINDER 5 200

So any thoughts on why compression is low on cylinder 2? One guy suggested it's piston rings but another Volvo tech said he has rarely seen bad rings on 850s. Your input would be greatly appreciated.

It is very uncommon for the rings to fail in Volvo engines. Adding oil and having the compression go up is an indication that the valves are not the problem. Oil can also seal a head gasket leak as well as worn rings.

Use a magic marker and note the coolant level when your engine is cold and hot. Then check and note the level of oil on the dipstick with a hot engine after turning off for a minute or two. Check at least once a week.

Oil can only cause white exhaust smoke if it gets into your exhaust in an unburned state, otherwise it will be blueish. Black is fuel. White is normally antifreeze/water which also means condensed water in the muffler.

Driving the engine 'hard' for 10-15 minutes lets the valves rotate and keeps them clean, which is a good thing. 'Hard' is above 2500 rpm. 5000 rpm is used to clean out carbon deposits.

AutoRx can be used to remove gunk and baked on oil deposits inside the crankcase and will help keep the oil separator clean, which then helps keep the PCV clean.

Klaus
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Proud owner of a 220S. If I had more room, I would have more Volvos.

Bad rings would likely cause blue smoke as the car would burn oil. Have you noticed a lot of oil consumption? And/or does the car use any antifreeze?

the fact that the compression jumps up when WET it almost assuredly points to the rings leaking, but i am willing to bet the rings are just stuck and not sealing right..
i would get the car running and give it the beans..put the transmission in low gear and go drive around and spend a fair amount of time with the engine above 5000rpm 10+ mins to get things moving..and then measure again..that has worked for me to work rings lose again..
or you can try autorx..a good product..

yessir - prime candidate for a good old Italian tune-up. If you've got good oil in it, and warm the car up first.

Give her a good Seafoam and water intake treatment too for good measure using the 'water torture'/suck-it-up-through-a-vac-hose method.

At any rate it won't hurt and you just might find it improves things.

If you do this be vey careful and use a VERY SMALL diameter hose. Maybe just 2-3 mm. Others have tried this using too large a hose and sucked up fluid too fast filling the cylinders jamming the engine and probably bending a con rod.

If you do this be vey careful and use a VERY SMALL diameter hose. Maybe just 2-3 mm. Others have tried this using too large a hose and sucked up fluid too fast filling the cylinders jamming the engine and probably bending a con rod.

Thanks to everyone for the advice! Much appreciated. I'll give it a shot.