Ok first off, I Di search and read the other threads. Tons and tons of them. But guess at my age, the brain gets confused more easily. Age old question on Merc crusiers. Which oils can i use be sides quick silver. Reason being I really dont want to pay the cost these days by the quart. And so I 'd like to get a 5 gallon bucket. I only boat may till september. And the boat has a 4 cyl. Merc.I/O, My car is a HHR that requires 5w -30 and My truck is a Suburban Ive always run 10W 40 Valvoline in. My question is. What would be a good compromise for all 3 if there is one.