Castrol GTX Diesel 15W-40

superk wrote:
I believe the diesel trucks in the fleet for the company I work for all use castrol.

Is there some reason why we shouldnt be using it? I know its a lower-grade oil, but apparently it was better than most of the 'bought in bulk' oils.

You are dead wrong on Castrol being a low quality oil. We have used it for years and it was a highly recommended oil By VW and Porsche back in the day. It could handle the high heat of air cooled engines with out break down. :R