My '78 sud 1.3 super is using a lot of oil, can't remember how much exactly as its been off the road for the winter, but more than seems reasonable. The exhaust is dirty grey, though not black, and is particularly so when the engine is cold, clearing a bit as it warms. There are no external oil leaks so I'm guessing something is worn in the engine, though it runs a treat otherwise. Does anyone have any suggestions of where to start looking? Thanks for any help!