Join Date: Jul 2008
Location: Railton, Tasmania, Australia
Re: Temperature Vs Mileage
I suggest you check the operation of the engine cooling system thermostat and possibly the temperature sensor. With EFI engines the fuel/air mixture is richened based on a number of inputs, coolant temperature being one of them. If the thermostat is getting tired and not closing properly then it's possible that the engine is running cooler when the air is cold, hence a richer mixture may result. This being the case, in extreme conditions the engine may also begin to consume oil due to the richer mixture tending to cause washing of the oil from the cylinder walls. Larger EFI car engines are known for this, my Nissan RB30 engine being one case. Also, colder air is denser air, which means more oxygen (21% of total air volume) gets crammed into the cylinder, so there is potential to produce more power. Testament to this theory is the fact that diesel engines run better in foggy conditions. EFI systems require cold air, as much of it as possible, that's why there is no air preheat system and air intakes are set up to get as much cold air as possible. Preheating systems were required for carburettors, to prevent freezing due to high velocities through the venturi.
1987 Yamaha TY250R
1991 Aprilia Climber 280
1988 K100RT (the pack horse)
2005 K1200LTE Light yellow metallic