I'm tempted. I've got a 94 C220 w/98k that's pretty bullet-proof and I really like it. I got an opportunity to pick up a 99 C280 w/86k and the sports package for about $8100. I'm torn, do I give up the known reliability, bird in the hand as it were, of the C220 for the features of the C280. I figure I can probably get $5500 for my C220, so it's about a $3k upgrade.
What has me nervous is all of the new stuff they added to the later model cars that raises the cost should the transmission go out or something else go wrong. I use this more as my comfort car and have something else that I use as a sports car, so I don't really need the upgrade, but it is a nice car.
If the '99 is in really good shape: go for it! 5 years newer for $3k as well as the engine & sport package. Something might go wrong with it...but something could go wrong with the C220 as well. I enjoyed my '94 C220 but it did seem to have to work pretty hard with just a 4 speed automatic; I never drove it over 75 mph. The 6 cylinder is a great engine; your gas mileage will likely be similiar as the engine not having to work as much.
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'87 300E: sold after 11years @ 230k & still on the road somewhere in rural Tennessee.
'94 C220 with 93k totalled 10/06 by hit & run broadsiding monster truck: not a scratch or bruise for me
Just verify that the harmonic balancer has been replaced as part of the US recall campaign. If it hasn't been replaced, make sure that you get it replaced ASAP. If it fails, it results in major engine damage.