To be completely honest, I don't really care about the do's/don'ts or rights/wrongs.
The simply question was how it's done. (thanks to those that gave useful answers
)
How can it be so difficult for everybody else to simply answer the questions that are asked.
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As for manufacturers not being able to get their cars performing right with all their own products. It almost certain that a fairly large percentage of drivers use shock oil / wheels etc that aren't made by the manufacturer of the car.
Why re-invent the wheel ?? (excuse the pun)