Coolant, brake fluid and service chemicals

Only in an emergency, and then get the system corrected. Water alone has no corrosion inhibitor and no anti-boil or anti-freeze protection, so topping up with it progressively dilutes the protection the system depends on — the water pump seal usually fails first.

Typically every two years regardless of distance. Brake fluid is hygroscopic: it absorbs water from the air, which lowers its boiling point. On a long descent, fluid that has absorbed water can boil and give a pedal that goes to the floor.

Organic Acid Technology coolant uses organic inhibitors that last far longer than traditional silicate ones and do not drop out as gel. The two should not be mixed — flush the system when changing type.

Only where there is a reason: a missed service history, visible sludge on the filler cap, or a vehicle bought used with unknown maintenance. On a well-maintained engine it is unnecessary. Never drive the vehicle on flush — idle only.