probably has a crack to leak that much in 10 min. By going thicker what would be your choice? For you short time idle a 10W-30 might help with a higher cold vis. Short term idle then shut off each day is not really a good; combustion creates water and complete warm up get's rid of it. If not warmed up enough moisture remains in the oil. I would just drive it to complete warm up then could let it sit for multiple days and repeat.