Re: Alfa 147 oil
That sounds strange to me - not being able to read the level accurately. My tip is this - when the car has been parked on a level surface for sometime, take the dip stick out, wipe it, and then stick it back in. Take it out, relatively quickly avoiding tapping it against the sides as much as possible (ie wiping it as you bring it up against the tubular lining), Then you should be able to see a distinct thick lining of oil indicating a level. To determine whether it is below the minimum depends on your dipstick. Some have bent/inclined dent being where the level should be, others just have two lines (lower being minimum and vica versa) and some being patterned to suggest where the minimum and maximum should be. I don't know exactly what the 147 dipstick looks like - but this covers most I have seen in several different marques. Hope it helps and isn't too obvious. BTW my 156 oil is quite dark at the moment and it sometimes adds to the difficulty of reading it, against a dark dipstick.
Every car differs in the amount of top up it requires so the dipstick is the only real way of determining whether yours need a top up. I don't think there is a science behind how much you should top up abtrarily.
You are right to keep an eye on it - its very important with all cars but Alfas seem to require more top ups than the average car from what I have read here.