Car: 1991 BMW 318i with M42B18 Location: Richmond, B.C. Canada Max. temp over past year: 28 degree C Min. temp over past year: -12 degree C Usage: Lots of short trip to school, 80%city/20%Highway I have been using Castrol GTX 10w-40 all year around for the car. Mainly because it was available at costco in 12L cases. What brand and weight would you guys recommend for my condition ?