I admit to being a bit perplexed when comparing the extended drain numbers for the various European auto makers. The ones that produce both gas and diesel cars all list LONGER drain intervals for DIESEL engines. I'd always assumed that diesel engines were actually harder on oil than gas engines, so what is behind the longer recommended drain interval for European auto diesels? Larger sump capacity? Do these engines utilize bypass filters, where the gas engines are just full-flow? Any ideas?