Whether you choose to keep your Mercedes or not firstly has to be a financial decision - if your budget allows you to keep it and run your main car, whether that is the Suzuki or the Citroen C4, then that gives you the freedom to choose. If you are considering keeping the Mercedes as a potential future classic, at 20 years old it is still relatively young to be gaining value and there are many examples still on the road, even if yours is one of the better examples. We would suggest keeping the car because you enjoy owning and using it rather than seeing it as a possible asset, as it is unlikely to gain any value for another five to ten years at least.