fuel enrichment to make it idle properly... Fuel doesn't vaporize very well when the cylinder components are cold so you have to dump a lot of extra fuel just to get enough atomized to combust. So I'll say that it does take more fuel when you start the car cold, but that enrichment falls off in gradual percentages as the engine temp climbs to 160F. No additional enrichment is used until the engine climbs to 214 degrees, then the ECU starts dumping 15% more fuel to try and ward off detonation since the cylinders are damn hot. So if your car is running hot, it will also eat a lot of fuel.