Keep a bottle of Diesel 911 around as well, good stuff for drying out watery fuel. If your '93 is like my '82 300D, there is no heater on the fuel filter. I also try to keep all diesel tanks as full as possible, especially in winter, to cut down on condensation. Mac's Antigel is also available at NAPA, I have a gallon in the basement that I got on sale, fortunately haven't had to use it!