Believe it or not, but if your engine has its oil filler cap removed then it could eventually do irreparable damage to the internals and the engine bay. Think about it - the cap is located at the top of the valve cover, which protects the rest of the engine bay from the oil that is spraying and sloshing around in the valve train. If your engine is losing oil, then the crankshaft, connecting rods, pistons, and other engine internals will lack the proper lubrication necessary to keep them running. Eventually, they will seize. And where does all that oil go? It ends up on all the other parts in the engine bay, coating your hoses, wire harnesses, engine block, water pump, etc. with oil that will attract dirt and dust. After a while, it will be impossible to get rid of. All this because the oil filler cap wasn't keeping the oil in the crankcase.
Using oil to lubricate internal combustion engines goes back further than the reciprocating engines we use in our cars. However, not all early car engines used oil pans to store the excess oil for purposes of lubrication. Drivers used to be required to continuously add lubricant to their engines as it was consumed and burned off. As engines became more efficient in the 20th century, the lubrication system required oil to be stored at the bottom of the engine block so the crankshaft could continuously bathe in it and distribute it to other parts of the engine. And since the engine now stores oil in the pan, it needs a way for it to be poured in and a way to prevent it from being ejected. That is the purpose of your oil filler cap.
Replacing your oil filler cap is not science. If your existing one isn't maintaining pressure, it's likely because of some sort of defect in it. It could be cracked, cross-threaded, or the flanged surface of the valve cover may be warped. Either way, when you get your new oil filler cap, make sure it is free of defects before screwing it on. Also, you may want to clean off the port on the valve cover so that you can inspect it for any irregularities as well.
Don't spend days, or even hours, looking for a replacement oil filler cap. At Car Parts Discount, you will find one that is guaranteed to fit your engine. Our product descriptions give you all the information you need to know to make an informed buying decision. And when you buy your new oil filler cap from CPD, you are sure to be completely satisfied.