@rozzzz
you mentioned two things
- engine oil get dirty sooner.
air intake has a filter on it and it doesnt let dust particles, so if you filter is of good quality, your engine oil doesnt get dirty camparitively sooner.
the filter of intake has a big surface area there fore it allows more air with a less resistance to enter the engine intake (throtle body)
- Hot air enters the engine engine.
positioning of intake filter during its intallation can avoid this problem as well.
normal air filter setup also takes the air from the same place where the after market intake gets air from. so that I also dont agree.
Main function of after market intake is to let more air with a less resistance and it works because of a bigger surface area filter. nromally after market intake have double surface area as compare to your stock air filter.