Radiator and wather heat?
And ofc wather temperature witch will influence MTBF.
Same could be done with oil temp and coolers

This could be implented in the weight, and a limitation of the coolers size regarding what the engine is buildt for(race car/smal eco car/truck/stationary), would be fun to have the option of air cooled also, to have the option for low weight, but poor cooling

This gives the opertunity for cooling of turbo's also, oil/water/both

Edit: added coolers size for clarification