Most petrol stations and their attendants offer the courteous service of checking your oil and water while filling up.
While it is a generous act to make the customer feel valued, from a mechanical point of view it is rather useless. Why? because all the oil is still sloshed around in the cylinder head and upper echelons of the engine when switched off. This means a full reading will almost always show.
Do it yourself
Oil can only be lost in an engine in two ways – through an oil seal leak at the bottom of the engine or directly through the exhaust. Of course this mostly applies to older cars that use more oil over its lifecycle.
The most accurate way to check your oil level is to do it yourself. The only difference is that you have to wait about 20 minutes for the engine to cool down slightly. This also allows enough time for the oil to filter its way down to the sump.
Checking the oil yourself also gives you an indication of how healthy your oil is. The last thing you want is pitch black or silver-coloured oil on your dipstick.
So if you have the time to do it yourself, familiarise yourself with what is going on under the bonnet.