5w-40 is kinda a niche viscosity. Had a tribologist tell me it was a solution looking for a problem. I used it specifically for one particular Anchorage truck fleet that didn’t have a bullrail available to plug block heaters in. Made winter starts easier vs 15w-40. And certainly reduced filter bypass time. The price premium was worth it, in that application. I experience no issues running 15w-40 in the Arctic when when using coolant & oil pan heaters.