Checking your bike over before you go out on it should form a regular part of your riding life. It’s essential for your safety. Barreling towards your favourite bend at a healthy speed is a bad time to find out that your brake pads are down to the metal or that your tyre pressures are way out, for example.
It helps you spot any maintenance or repair tasks which need doing. It’s useful to know that you can mix any type of engine oil with any other. However, it’s best not to. If you add mineral oil to a bike running synthetic oil, for example, the performance of the oil will not be as good.
In an emergency, it’s OK, but as a general rule, always top up the same type of oil, mineral, semi-synthetic or fully synthetic that is already in the bike.
The same goes for brake and clutch fluid. Pre-ride checks only take a few minutes but they will help you avoid accidents and will also help you keep your bike in top condition.