When I bought my Buick GN new, I'd use Mobil 1 and a new filter every 2000 miles. I drove it really hard like it was meant to be driven and always try to let the turbo cool down, but still the 2000 mile change. The trans went out at 100,000 miles but never had any problem with the motor. Wish I still had it. Wish a total Mobil 1 and filter change was still $25. That seemed really high back then. HaHa.