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.
Grout can completely change the appearance of a brick wall - for the better, but also for the worse. So find out what you should be guided by when choosing a brick grout to make the effect satisfactory.