From the attached photo can someone explain what is the purpose of this? I know it is not the oil strainer ? It does have a very very slow drip when the engine is warm then stops. From tech books it has 2 sealers ? But am confused. Also wish to change my own oil, went to several auto shops ,there is synthetic oils, mineral oils and so on ! Can some one recommend which oil type. brand and grade for my 2 litre motor.