90WLSP36 Smoke and heat

[williamcharrison]

Just recently my bird began to blow blue oil smoke when it was cold.
This symptom has gradually gotten worse over the last 3 months.
After warmup the smoke disappeared (after 10 min or so). I took it
to the local Cat dealer who discovered that the turbo was shot.
He replaced the turbo ($4000.00 +) and the oil smoke is worse than
before, what's more, the engine will not heat to above 160 deg.
whereas before it ran at 190 deg. The dealer says I have to run it
hard to clean the engine out but I have to get the engine temp up.
The oil temp also does not go up over 170 deg. Does this sound like
symptoms of a stuck thermostat? If so, how hard is it to replace and
what would cause the excessive oil smoke?

Thanks,
Chuck Harrison
Akron, Ohio
90 WL SP36