I'm about to do an oil change on my 4/4 1.6 TI VCT. I've been thinking about the old threads on oil here. Currently I have a guest from Chicago, a friend who works in the audio industry as an engineer. He also has a friend who works in the engine development at Ford USA. I asked his advice. My guess was that shear strength means that the camshafts are protected. Ford oil do not do it just because they want to reduce the overall fleet gas consumption. You have a little more resistance with a shear strength and therefore a little higher petrol consumption but a far better protection of the cam shafts. The Ford spec oil has lower friction but when the engine is running at temperature the oil loses its protection (partly) and the film is too thin. Especially if you drive sporty with a lot of high revs as I like to do so.
And here is his fresh answer to my Q, even if he works for Ford:
„Definitely upgrade to a thicker hot weight oil 5W30 or 5W40 even for long extended periods of high rpm. Also use a good synthetic with high HTHS (shear strength at temperature)“
So I know I now will test a good oil, more so of Mercedes HTHS specification than a Ford specification. I will post how it works.
