Your "average" 4 cylinder'd car (per your examples) rev higher than 6k before redline and the 5.0L don't even do that. It is around 5,600 rpm or so right...but starts cutting off even before then. Those toyota's usually are around the 6,500 rpm mark or so on "average". Plus the cars your talking about...they are usually newer and do they have the same rotating weight as a 5.0L for example? same valvetrain? same car weight? same need? same piston rings? same pistons? etc. Just a few...
I wouldn't idle my car around (not enough oil coverage). Bad example there
I made it for 2 pages,,LOL,,I'll read the rest tomorrow!! I have a 1995 Jeep with the 4 cyl. At 70mph its at 3000 rpm,I usaully do 75-80 so its above 3000rpm..It red lines at 5000rpm.The motor has 259,000 miles on it and it runs like a champ,doesnt leak a drop of oil,it gets a quart low at about 3000 miles(rite around oil change time)
What Michael is trying to say when you are cruising on a highway at 3000 rpm you motor isnt using much energy to maintain that speed,so its not really hurting anything.Your worried about friction,well thats where synthetics come in Heck regular Dino oil is fine,as long as you change it regularly and your level isnt low!!