On three occaisions, all when the temperature has been below 15 degrees F, my '98 Jetta produces clouds of blue smoke for several minutes, up to a 1/2 hour on one occaision. Monitoring of the dipstick shows the level dropped about 1/4" after the last episode. This seems to happen about once a month. The car has 43K miles on it. I bought it with 33K on it this past September, so it had mostly been used for short trips. Delvac is pretty expensive to be blowing out the tailpipe - can anyone tell me what's causing this? I was thinking a bad turbo oil seal, but if it was that, wouldn't it stay bad all of the time?