In a word...YES!
Just change your oil often and throw in a good fuel injection cleaner to the gas tank every 6 months or so if you do a lot of city driving and be done with it. It has been determined by a lot of different State consumer organizations that those products either do nothing or, even worse, do more harm then good with the by-products they produce in your engine over time
The old saying holds "If its to good to be true..." you know the rest.
Save your money for a good tune-up and what ever you do don't run your engine with just one bottle of prolong in it and no oil
88 230E (W124)