The car will use more fuel, this is because it can't breath properly affecting combustion within the car and the exhaust pipe will be black quickly (when you rev the car u even can smell the fuel right from the exhaust pipe).
Poor flow of air into the vehicle. Replace the cabin filter every 30,000 miles.
Yes it does the proper air flow that the engine requires is slowed from a dirty air filter
Some symptoms are; Rough idle / running rough / feel like you're running out of gas / it even may be bad gas, or water in the gas, instead of a dirty or bad gas filter. If you decide to remove the gas filter, be careful. After removing the old filter blow air [in the direction or the arrow à on filter] with your mouth thru the old filter if it's hard to blow air thru the filter it clog up no good, but if air blows right thru with no problem then filter is good. But since you already have filter out change it anyways.
No. A dirty cabin air filter would restrict the air flow from the heating, air conditioning and ventilation systems.
Yes!
a dirty air filter or a dirty fuel filter will cause a diesel to smoke
No, it causes a restricted air flow, causing poor performance and fuel economy.
When it is dirty.
If it is that dirty, replace it.
When it is dirty.
A dirty air filter will cause your car to loose horse power. You may loose acceleration and torque.
When it is dirty.When it is dirty.