So recently I've done two things, one of which was joining BITOG and the other was receiving a 1993 Buick Park Avenue Ultra S/C. Now, it had been lurking about for 3 years in a backyard with unknown oil in it, and an unknown maintenance history (came from estate sale in my home area) and I ressurected it. During this fix and tune thrash, I threw in Castrol GTX High Mileage 5w30 (I get it cheap through my part-time job as a parts counterperson)/w/ the usual K&N oil filter (which i've used on most of my past vehicles with success). However, using GTX HM went against my natural instincts to use an "affordable" quality synthetic oil such as Q HP, RP, or PP. But then, on the other hand, I was concerned about possible leaks and such so that's the route I went.. Now for specifics. The car is indeed a 1993 Buick Park Avenue Ultra /w/ the 3.8L supercharged V6. It has 280,000 kms, and appears to be running well post tuneup. It also appears to be "sweating" from both front and rear valve cover seals (transversly mounted) after 1500 kms, and the GTX HM has minimal carbon build-up in it showing when checked with the dipstick. Now three questions, First, should I be giving it an early oil change? The car is bound to turn up a bit of crud on the first oil change post-ressurection. Second, should I switch to a quality synthetic? I'm just afraid the detergent qualities of a good synthetic would increase leakage at the valve covers (the seal swell properties can't be THAT good). Plus the car has NEVER seen synthetic before. In fact I doubt it even saw the recommended premium fuel as it's not readily availible in the area where the car was previously driven. Third, should I stick with a 5w30 vicosity? I drive the car almost daily in our excellent Edmonton winters (anywhere from -10 degrees celcius to -40) and it is rarely (if ever) plugged in (street parking). Comments and suggestions are encouraged, I want to hear the expertise of many.