Just used this caltex havoline 20w-50 oil on my 1996 nissan sentra ga13 engine with 139,100k on odometer, parang naging pigil yung takbo, I have to step more on the gas to get better acceleration, (oil filter and air filter were replaced & flushing was done during the oil change). Unlike before when I used the shell 20w-50 helix (in the red container) there's no hesitation on acceleration, Di ba same lang viscosity nila? Need advice kung Ok lang ba na gamitan ko nang semi synthetic like castrol or shell yung 15 year old engine? kung 10w-40 oil wala ba maging problem? Btw there's no oil leak in the engine & i never add oil during change oil intervals.