Why on earth would that be difficult?? Just go to the next Mercedes dealership and ask for the correct spark plugs for your car. This is like saving a dime but wasting a dollar.

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600SEL '91
300E 4Matic '88
240D '83
280SE '77
350SE '73
The most complex systems can fail in the simplest way.
Contra verbosus noli contendere verbis, sermo datur cunctis, animi sapientia paucis.

i don't believe in the lord! He's never bought me a Mercedes Benz.