sounds like the thermostat, a bigger radiator does cool better but the thermostat should still cut off coolant flow so it will get to operating temperature regardless of how big the radiator is, if it is the electric fan switch than highway use would not matter because the air is already flowing accross the radiator. thermostats are cheap and easy to replace, i would just try one. another alternative is just to place something accross a portion of the radiator, large trucks usually do this in very cold weather, just make sure it doesnt overheat if you cover too much of it.Why my car lasts a lot to warm up the engine and in highway speed temperature drops?
Radiator capacity has nothing to do with it. Its the function of a thermostat. When the car is warming up and any time the engine temperature drops below the thermostat setting the thermostat is closed and the coolant is circulating around the engine bypassing the radiator, this this is how the engine temperature is controlled.Why my car lasts a lot to warm up the engine and in highway speed temperature drops?
this is because of the electric thermostat, not the mechanical one. the electric thermostat is controlled by the ECU. my honda does the same thing, but I've been too lazy to fix it.
