I am strongly considering moving about 85 miles from my place of work. The commute is a long one and will mean climbing a serious mountain pass TWICE every day. What I want to know is what opinions are regarding the VERY best oil for this task. I will travel about 4k miles per month in all kinds of weather. The pass is steep and will be hot in the summer. My average speed on the commute will be about 70mph. My vehicles are as follows...2002 Ford Ranger 4 cylinder 5 speed manual, 2004 Mercury Grand Marquis, 2008 Ford Mustang GT. Cost is no factor.....protection and a 5 or 6k OCI is my main goal here. Synthetic is a given, and if any of you think a higher viscosity would be better protection please state reasons why. Thanks for the help.