Im wondering if I were to add a quart of 0W-20 Synthetic (Im not sure yet if its full or a blend yet, waiting on a reply from Petro-Canada) to 5W-20 Dino. Both will be the same brand and the crankcase capacity is 4.2 qt. I'd do this over the cooler months of the year mainly as an aide to cold starts because although I'll will use a block heater when its 5 deg F or colder, Im unable to plug it in at work and it does draw a lot of current noticeable on my utility bill