'01 CLK430 Cabriolet - puff of smoke at startup?
 

I have twice noticed that my CLK430 Cabriolet with 35k miles occasionally emits a good sized puff of whitish blue smoke. Maybe once every 10 starts. Any cause for concern?

Could be a leaky injector.

most likely Valve guides normally when you drive the oil is pumped up to the top of the cylinder head, upon shutdown if you have too much tolerance in valve guides the oil will "slither" down the valve stem into the piston and wait there held by the piston rings until you crank it up and burn off on initial startup, hard to belive in such a low mileage car, I would switch to Redline Synthetic straight 30Weight oil and see if that corrects the problem