must be connected in parallel, rating [24]

if connected in series, the rating will become even worse than that of a single cooler rating [55]

the rating is derived from the time spent warming up the engine from 70 to 90 degrees (the slower the better) and the time spent cooling it down from 90 to 70 (the faster the better). Absolute numbers give an idea of the difference in efficiency, but this does not mean that a rating of [40] is twice as good as a rating of [80]

for liquid liquid exchangers, water was used with an intake from the sea with two large pumps (in, out)

for air exchangers, air was also pumped through one large pump for in and out

under different conditions, such as heating rates, etc., the numbers may change, but an electric radiator is always a winner