1996 Volvo 850 Turbo with valve seal problems

I bought a 1996 Volve 850 Turbo two years ago. Currently, it has 240K. My problem is that it is belching blue smoke and my mechanic says that the engine has to be rebuilt because the valve seals are gone. I’ve put quite a lot of money since the purchase of the car into brakes, tires, muffler, etc. and the cost of rebuilding the engine is pretty high, @ $3,000. As a result, I would like some advice as to whether to proceed with the rebuild or buy another car. I’d appreciate any advice on whether a 1996 Volvo 850 Turbo is worth repairing? Thanks, CB

It does not sound correct that the engine needs to be rebuilt just to replace the valve seals, are there other issues with the engine?

How has he confirmed this? I wonder if the oil seal in the turbo has failed which will introduce oil into the engine. Does it only occur at higher RPM, eg under turbo boost? A turbo replacement is significantly cheaper than $3000.

I was also told it was the rings. They did a compression test.

The exhaust smoke occurs as the car is shifting from gear to gear. This is when it is the worst. While idling there is some smoke but not very much.