I had been using a witches brew of 3.5 quarts of M1 0w-30 with 1.0 quart of M1 15w-50 in both my GM 60 degree V6 engines; a '00 3400 and a '01 3100. I seemed to work well enough. It kept them quite at startup, did well on cold Winter mornings and didn't thin out in the heat of Summer after just a few thousand miles. In looking at the viscosity specs of the GC 0w-30 off the German website, both the 40C and 100C numbers seem to pretty well match those of my M1 witches brew, as well as those of the Amsoil 5w-30 and 10w-30 and Redline 5w-30 formulations.
We all now have to live in the aftermath of the M1 marketing debacle and the fact that most stores have dropped the M1 0w-30 selection simply because there isn't enough shelf space for all the weights/styles. Since I didn't want to have to use the M1 0w-40 oil in these engines and risk a 2-3% loss in fuel economy, I finally decided to give GC a try. Then I read here that the old yellow label Made in USA 0w-30 is resurfacing and maybe in fact replacing the real red label Made in Germany 0w-30. Say it ain't so!!
So yesterday at lunch, I stopped into my four local AutoZone stores and cleaned them out of all the red label Made in Germany bottles. I got 41 quarts in all. I didn't check the born-on date codes (shame on me), so I will have to do that this evening or tomorrow. Hopefully I didn't get too many of the M050 batch bottles with the amber formulation. When this is gone I guess I will go back to my witches brew, as long as I can find the new M1 EP 0w-30.
I also have in stock in the garage;
15 quarts of M1 5w-40 Truck & SUV
9 quarts of M1 0w-40
and 5 quarts of M1 15-50 all for the "other" engines
as well as 1 quart of straight 30 weight and 2 quarts of 10w-40 Valvoline and a 6-pack of MTD 50:1 2-stroke oil, all for the power equipment.
You know this is a sickness...