Do not trust a gauge which unfamiliar to you. It is always better to carry your own tyre pressure gauge of a good brand. The accuracy may be wanting but it is the consistency that matters, as long as you are aware of how much your gauge is over or under reading. Determination of the actual pressure appears to be complex but there are basic principles which, if adhered to, make the determination easier. Always remember that most tyre pressure quoted are absolute minimum pressures, with the tyres in a cold condition.
More air is required to meet heavy loads and fast driving conditions.
The first step is to establish the size and type of tyre on your car. This can be done by observing the sidewall of the tyre where the size and the tyre, such as 7.50 - 14 or 185 SR14, will be moulded. 2.Heavy load condition - which is more than 2 or 3 passengers plus luggage. The third step is to refer to your owner's manual. In it are recommendations for the pressure to be used under the motoring conditions you have decided upon.