You should check the oil levels of your car regularly and especially if you are going on a long journey. Driving your car with very little or no oil can cause significant damage to the engine and can be very costly.
If you leave it till the last minute to put oil in your car you may find that you have to pay over the odds for it as motorway service stations and even some petrol stations within towns or cities charge a lot. I recently compared the prices for oil and was shocked to find out exactly how much extra motor service stations charge.
I was quoted £18 per litre for oil from the service station and after looking at retailers such as Halfords, that were charging £10 per litre was amazed to find that my local garage (independently run) were quoting £6.75 per litre. That is less than half the price of the motorway service station.