Hi,
I am using Mobil1 Synthetic 15w50, and the engine is very happy with it..
I do not drive the car as daily driver, and I hardly put 4 or 5k /year..
My question, is it OK to extend the interval for one year, if mileage under 5k or so??? should i replace oil filter in between?? what is the max. time after which the oil gets bad even without driving the car??(synthetic oil)

thanks