actually colder air would lead to denser air/more air. requiring more fuel to keep from running lean. it would result in an mpg drop
same as if you put a cold air intake on, more air so more fuel required
add on a blower/turbo,more air so more fuel required
Denser air also provides higher compression and therefore more power per fuel injection, or. stroke What you said is true if you run both engines at same speed. But a turbo engine for instance, can generate enough power at 2000 RPM that a non-turbo one generates at 3500 RMP. So overall, you can theoretically still have higher mpg. However, in the the real world, engine design constrains and cost generally make turbo gasoline engines of regular cars less efficient than the equally sized naturally aspirated variant. This is not due to an inheritor inability, but because of cost and design. Most turbo engines on cars are designed to run rich on fuel when turbo kicks in. So they actually have incomplete burning and are less efficient. They program these engines run rich because a complete burn would generate more heat and pressure and put more stress on the engine, and they would also be very prone to pre-ignite and knock if a lean air-fuel ratio is used. An engine can be designed to run lean with turbo, but the additional weight of beefed up engine and cooling system, plus the cost, makes it illogical produce such an engine. It is a lot cheaper to make a slightly small turbo engine or slightly large turbo engine depending on if you want more economy or power. Overall, turbo diesel engines (where engine knock is not an issue) and turbo gas engines of prop airplanes (which are operated at very low temperatures) are more fuel efficient that equally sized naturally aspirated variants. So it is possible to design such an engine, but it is not cost effective for a regular car.
It wont work the same way for cold ambient air, except when engine when its cold. Once the engine heats up, it will also heat up the air going into the combustion chamber, so the compression will more or less be the same regardless of ambient temperature. Cold air intakes try to get over this but the improvement in power is rarely more than 1% since the majority of the heating and expansion happens once the air hits the hot engine block around the valves. And since engine block temperature is more or less the same for a heated engine regardless of weather, ambient temperature of the air is negligible. ECM does inject more fuel when the engine is cold to run a rich mixture. Because that is the only time when air going into the combustion chamber is colder and denser(and cutting back the air going into the chamber would cause knocking).
correct, and that compensation for colder is more fuel.
Not necessarily. Any engine with a MAF sensor can also reduce the air going into the cylinder. And its easier to reduce the air going in than increasing the fuel. Because increasing the fuel would cause the engine to generate more power per stroke and it is a lot more difficult to control engine that is generating variable amounts of power per stroke than one that is generating equal power. Otherwise the the car would speed up and slowdown on its own without you giving or cutting the throttle. Like I said before,more fuel is injected to a cold engine to run it rich, and this is to prevent knocking.
I think the main difference in drop in mpgs in cold weather is due to longer period engine runs rich and the fact that colder air is denser and cause more drag. Especially at higher speed like in your case. Also check if you state switched to winter blend gasoline which has a bit less energy.