If you had a high mileage (87,000) VW Passat with the 1.8 turbo, which oil would you use in it? I have always used Castrol GTX in my cars but just recently got this one. The dealer has always serviced it and they are still putting 5W-30 of some sort in it. BTW.. the car runs great but I was thinking with that mileage that maybe a 10W-30 would be better.