although from your first post I did not. I am not sure what you suggest a car company do, however. I doubt that people would invest in the time and effort you suggest to establish the proper moment their spark plugs should be changed - because it does not seem economically viable to do so. All the car company can realistically do is publish a schedule they think is right. Given your expertise (which I swear was not apparent from your first post - I feel totally snookered by that!) I accept that what you suggest is the best way for everyone to squeeze the last bit of life out of their $5 spark plugs, if they are so inclined. I am unaware of M-B policy as far as their Starmark warranty is concerned, but in the extreme case of someone failing to ever change their oil and their engine blows up as a consequence, I believe that person would have a very difficult case to prove to collect on the warranty. It would therefore certainly be a sensible policy to void the warranty if all recommended maintenance was not performed at close to the recommended intervals. It would be your choice as to whether the chance of voiding the warranty is worth the obvious savings involved in getting maximum life out of your spark plugs and ATF (see my tongue in my cheek here).

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Chip Johnson