Phill, mine has about 200k on the chassis, with about 15k on a Benz factory rebuild. The previous owner decided to drive the original engine around without any water. Since the engine, injection pump, etc... is new I wanted to get the algea out fast. Kidding aside, do wear some plastic gloves when you use that stuff. It is just foul and stays in your skin no matter how much you wash your hands.
Regards - Luke
How many miles on your 78?