I picked some of this up via the rebate and I'm curious if it's safe to use it and then go back to my M1 for the winter. Will the seal swellers be an issue? I still have some M1 left over which I planned on mixing with some Mobil Drive Clean Plus and use it here on out after the MaxLife...... but since I can't find that and M1 is still a reasonable price I guess I'll stick with it. So run the MaxLife, then go back to M1.... or keep running M1 and use the MaxLife in something else, give it away, ect? BTW, the engine is a GM 2.4 DOHC with about 84,000 miles. Consumption is not a concern, so I see no need for HM oil.... just couldn't resist free.