[Bob's944]

Diesel engine oils are approved to go into EXTREMELY expensive very high tech turbo diesels that are designed to run for a million miles. They have more certifications and approvals than the very best gas engine oils. 15w40 oil is 15w40 oil, how well it holds up to temperatures and pressures seems to be very different. These oils are approved for all gas engines too, I just don't think the oil companys want everyone able to have their oil last so long. I have definately noticed a diference.