At the last maintenance (64,000 Km ... just a month ago) I declined these items which MB recommends every 4 years. My wife did not agree with my decision in this regard. Thinking that we should not second guess MB's recommendations.

I had to go back to the service shop this week to have the cause of a contineous "Check Engine" warning light investigated. It turned out to be the Cat CO2 sensor.

A Fuel guage sensor and (more BAS/ESP warnings) a Brake booster travel sensor were covered under the extended warranty on this visit to the shop.

I had them do the Spark Plugs and Fuel Filter Change and sure enough the car seems peppyer now in highway passing speeds and snapier off the line. The cost $ 696.11 Canadian. Ouch! But good for another 4 years or 90,000 Km.