welcome to mercedesshop and welcome to 400E ownership. I have had mine for a little over 4 years. Got her at 73K miles (now have 147k) and the records were complete but details were abbreviated. Like you are considering, I baselined the car with 100% new fluids. Rather than changing to synthetics, I stuck with a standard 15W40 oil. As far as tranny, brake, power steering and coolant, I replaced and continue to maintain the car on MB fluids. The previous owner followed the bare minimum mntc requirements stated in the book. Since I have owned the car, I follow a much more aggressive mntc schedule. oils changes every 3K, coolant, power steering and tranny every 30k and brake fluid every 2 years. plugs and air filters every 15k.

my mechanic is pro-synthetic primarily in cars will lower miles. He suggested that transitioning from standard petrol based fluid to synthetics can often cause your higher mileage seals and gaskets stomach upset.....leaks and the like. I am not one to refute or support that advice but I can tell you I have been 100% satisified with sticking to good 'ole oil and OEM MB fluids.

enjoy the car and the website...lots of great info from some very knowledgable members.

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Jeff
'87 300E
'92 400E
'06 ML350