As things start to chill down here in Atlantic Canada, the 15w-40 starts getting rather thick. My past experience with Diesel VW's was to use 10w-30 in winter and 15w-40 in summer, as long as it was true Diesel oil. I don't plan to run Pearl after first week of December- she won't come out of the barn again until end of April, but cold cranking conditions are already getting cool here. WE are blessed (?) here with the Irving family empire- perhaps you've heard of them? Anyway, they make a fantastic Diesel oil called IDO, and IDO Premium, both available in 10w-30 and 15w-40. Always has been trucker's choice up here, although Pearl is my first Merc, and she's pretty old- I'll just see how she likes having the thinner blood this time of year. All of the big Irving truck stops have what they call the "Diesel Room" where the bi rig drivers can do everything from take a shower to get new tires for their rigs, and there's plenty of big jugs of IDO to be had

Dave