It's been mentioned that the VW 502 spec requires very demanding high temp/high load testing in a test that runs for 248 hours during which no makeup oil is allowed. What I would like to know is whether or not the minimum HTHS of 3.5 must be maintained until the end of this test or until the end of the suggested end of the drain interval for any particular VW/Audi vehicle. If in fact, the HTHS may be lower than 3.5 during or after the test, then a safety margin must have been taken in account, and it would be good to know what the actual minumum HTHS figure is. My question is, must the minimum HTHS of 3.5 be maintained during the above-mentioned test or during the entire drain interval in order to make this oil eligible for VW 502.00 approval? If the answer is yes, then how did M1 0W-40 get approved, since it reportedly thins out a lot. If the HTHS of 3.5 is only required at the beginning of the test, then this figure seems pretty meaningless.