An oil type air filter can cause contamination of the MAF sensor, which will:

An oil type air filter can indeed lead to contamination of the Mass Air Flow (MAF) sensor, which can result in a lean condition in the engine. When the MAF sensor becomes contaminated, it does not accurately measure the amount of air entering the engine. This inaccurate measurement can cause the Engine Control Unit (ECU) to miscalculate the required amount of fuel for combustion.

In a lean condition, there is an improper fuel-to-air ratio, where there is too much air compared to the amount of fuel being injected. This can happen because the contaminated MAF sensor may send a lower air intake reading to the ECU than what is actually present. Consequently, the ECU will reduce fuel delivery in response to the perceived lower airflow, thus creating a lean running condition.

This lean condition can lead to multiple issues such as higher engine temperatures, increased emissions of nitrogen oxides (NOx), and can even cause potential engine knock due to insufficient fuel for proper combustion. The other options do not directly relate to the contamination of the MAF sensor or the resulting lean condition; thus, they are less appropriate in this context.