Originally Posted By: buster
Mobil 1 5w-20 came out in 1974.
They also made the first available 0w-20 in 2001.
Don't know about the specs on this old 5W20, but they said it was good for a one year or 25,000 mile OCI. They also said it was the equivalent of 10W40 in dino oil. I don't remember when they came out with the 10W30, but I took them at their word and used M1 up until I retired in 2001, usually an 18,000 to 20,000 OCI. Never had an oil related problem. I went back to dino for a few years as I was not putting nearly as many miles on my car after retirement. Lately, my yearly mileage has increased to about 10,000, so I have changed back to M1. I am using M1 10W30 High Mileage formula