I spoke with a representative at Penray today about whether to use Pencool 2000 or 3000 in our cars. For our purposes, if you are running straight water, use Pencool 2000. It will provide corrosion protection and lubrication for the water pump. If you are running glycol antifreeze, use Pencool 3000 if you want more corrosion protection and to extend the life of the glycol. There is also a Pencool 4000 for use with the newer long life coolants.
The “for diesel engines” on the 2000 is just referencing it is safe for diesel engines, not that it should be used in diesels and that 3000 should be used in gas. Both are a cooling system additive for engines including car, truck, stationary or marine. These are products primarily for use in fleet applications, but will work in our cars also.