They are fairly good, though probably a little too old to find their way onto Mercedes Benz where they could be sold as certified pre owned.

That means you need to inspect it VERY carefully, best by a professional mechanic who is familiar with them. if it is being offered by a private party or a non Mercedes Benz car dealer. Avoid refugees from freeway pileups and rust cars, or any that show neglect, in lack of repairs, or maintenance.

Having books and records is a great plus in that situation, to see how the car has been kept up. I hope you realize that with these, there can be issues, such as rust, bad spring perches, electrical and computer problems, as the quality control and build quality is generally believed worse than the W124 model run, that preceded this one.

A good '99 E420 will be very fast, confortable, roomy and pleasant to cruise in. 90k is very acceptable mileage for a car that old. Aggressive bargaining might yield a good deal on it, as the market is not especially "hot" for cars with big V8 motors on them, these days....

Frankly, the '87 300E is a Mercedes Benz with a far better reputation than the W210 you are looking at, with respect to quality control, build quality, logevity and durability, simplicity and ease of maintenance.

If yours is not a basket case, and the mileage is under 200,000 it might make a lot of sense to just fix it and keep it.

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1991 560 SEC AMG, 199k <---- 300 hp 10:1 ECE euro HV ...

1995 E 420, 170k "The Red Plum" (sold)

2015 BMW 535i xdrive awd Stage 1 DINAN, 6k, <----364 hp

1967 Mercury Cougar, 49k

2013 Jaguar XF, 20k <----340 hp Supercharged, All Wheel Drive (sold)