What 5w-20 oils are heavier, like closer to 5w-30? Am driving from NW Indiana to southern Florida next month, and will be down there for a couple of weeks and then driving back. So lots of highway miles and hot temps. Have been using what ever 5w-20 is cheapest, changing at 5000 miles using only mc filters. Vehicle is a 2008 F150 with the 5.4, and has 55,000 miles on it. Thanks.