[oil pan 4]

Do diesels like cold air or warm air?
Its all a matter of perspective. Diesels need cold air on warm and hot days to give the most power and fuel economy but on cold days you don't want the intake air to fall below -5'C to +10'C because then you don't get enough adiabatic compression heating to light off the fuel, this all depends on the engine and its compression ratio.
Cummins recommends that for their stationary industrial engines that if their engine will be operated in -5'C or below that the engine have an enclosure and draw its intake air from inside this enclosure. Once it gets much above freezing the air can be drawn from out side the enclosure.
Your intake air needs to be with in a certain temperature range.
With too much heat in the intake you waste energy by creating excess heat from compression, this excess heat is just absorbed by the cylinder head and piston and does nothing for engine operation.
Ideally you get 500'C to 700'C when you compress the air in the cylinder. If your air is too dense and too hot your compression heating could be as high as 2000'C, obviously it will not get this hot because some of the heat is absorbed as it builds. But you still do the work to heat it that much and get nothing in return.