Any partially-used bottles of motor oil, brake or transmission fluid may be used for as long as three years after purchase. However, the product should be capped tightly and stored in a dry place, away from moisture. What kind of oil would you recommend for my car? Check your owner's manual for the recommended weight of oil (such as 5W30 or 10W30). If you do not have an owner's manual, or need additional information, check with your service station or  contact Shell Helps. What do the numbers on an oil bottle mean? One of the first things you see on the label of a bottle of oil is a group of numbers such as 10W30. The numbers refer to the oil's viscosity, or thickness. The first number ("10" in this case) tells us how well the oil will flow when it is cold, and if it will stay thin enough for easy starts on cold winter mornings. The "W" tells how well the oil will flow when it is cold, and if it will stay thin enough for easy starts on cold mornings, particularly in winter. The second number ("30" in our example) indicates how well the oil will maintain its thickness at high temperatures. Why should you change more than the oil filter? Why is it also necessary to change the oil? The engine tries to keep the gasoline in a separate area from the oil during engine operation, but due to fluctuations from low to high speeds, and cold to hot temperatures, it is impossible to assume that no gasoline will be passed into the oil. Also, condensation from temperature extremes will create water, which ends up in the oil. Dirt and sludge are removed by the oil filter, but the only thing that removes the other unwanted and damaging fluids is a complete oil and filter change. Oil filters come in many different shapes and sizes. Why? Filter design is based on many factors. Most car manufacturers design the engine to meet certain specifications involving the clearance around the filter, the type of threads used to screw the filter on, and the filter's inside and outside diameter. Most of these specifications are based on how much oil is being pumped through the filter, the pumping pressure, and the volume of oil being filtered. The length of the filter will also vary from engine to engine, so that the clearance required to take the filter on and off the engine does not exceed the amount of space available in the engine compartment.
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