It is clear that the car manufacturers switched to thinner oils, only after being forced by the government to meet arbitrary fuel efficiency (CAFE) standards. This has all been done at the expense of engine protection and longevity!
Good article on the pros and cons of running "thin" oils:
http://www.machinerylubricatio...0Economy%20vs.%20Wear
Seeing we are doing product commercials here....my advice is that if you insist on believing Ford and running 5W20, that you use Red Line ester synthetic. Not only is it API SG/SL/SM (SG is almost impossible to find these days...except in motorcycle oils!), so that means it has a great additive package to protect high pressure areas like the cam. Also Redline has very high film strength. A typical Red Line oil has the film strength of the next higher weight of oil. In other words, even though you are running 20 weight, you are getting the protection of a 30 weight.....
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Southern California Deserts and Mountains....
Desert: 450R, 400EX
Technical Trail: Rancher 420 and 350 4X4's
Kids: Two 250EX's and TRX90
Dual-Sport Bikes: KLX250S and XT225
Past rides: 300EX, 2wd Rancher 350, Recon, TRX90, Z400, LT160, LT80, Warrior, Blaster, CRF230F