Even though hydraulic oils are made to withstand significant heat, and can even be heated up to their boiling point and still maintain their consistency and handling characteristics, they should not be allowed to get too hot they will break down, and the viscosity will increase dramatically, and they will lose the ability to lubricate moving parts, either of which can lead to an expensive repair or a mechanical failure.
Every few years it is worth doing a minor refresh of your house or apartment. However, painting often poses problems, and at the root of these problems is an improperly chosen paint roller.
