My copy of Haines says to use Dot -3. Does it matter?

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dannyf
1984 Mercedes 300 SD 214 K miles. Runs on WVO ~ 22 mpg over 8 K on WVO
1997 VW Passat TDI 156 K miles. Uses biodiesel and diesel. ~ 41 mpg
1996 Mercury Villager gasser. ~ 20 mpg