If you open the oil filler cap on your ICTDI whilst the engine is running, should you experience negative pressure or positive? I.e. if you remove the cap and then hold it gently against the threads, does the cap get sucked down or lightly blown away from the engine? I would have though the cap would be lightly blown outwards (due to a bit of pressure passing by the rings and the engine breathing). Now.. on a hot engine, should it be spitting oil out at you?! Not huge gobbings, bit little spittles accompanied with visible oil vapour?