If the oil light comes on when you're on the road, you should pull over as soon as it's safe and turn the engine off. While you're on the side of the road, you should check the oil. If it's low, go ahead and add some engine oil and see if it goes off. If not, it's time to take it to the shop.
Part of the Smart grid glossary: An ampere hour (abbreviated Ah, or sometimes amp hour) is the amount of energy charge in a battery that will allow one ampere of current to flow for one hour. An ampere is a unit of measure of the rate of electron flow or current in an electrical conductor.
Technically a battery has a certain number of joules of energy available but no one specifies them that way. What is usually specified is the ampere-hour capaciity. Ampere-hour capacity is the product of the current drawn from the battery and the time (in hours) over which that current is drawn. It is important to know the specific load the battery is experiencing when these numbers are being determined.