If the piston is the heart of the shock then oil is the blood of the shock, and the better the oil the better the performance. As in all oil, shock oil sees its amount of abuse and must be replaced or maintained on a scheduled service, by doing that you allow the shock to perform better. Let’s look at oil, we have two kinds of oil synthetic and mineral. Synthetic oil is a man-made product generated in a lab and uses soaps to add lubrication to the product, where mineral oil uses fat to lubricate the product. Both oils
have their plus and minuses, both
both oils have air in them, and both oils are manufactured by an oil company. With the introduction of synthetic oils to the market and the benefits, many shock companies started using synthetic oils. Over time we’ve learned more about synthetic oils and synthetic oil manufacturing and have come to realize that a mineral based oil or even semi synthetic oil is better for a shock. This is because of the amount of air found in the oil, all oils have some air in them, and that is not good for a shock. When we started using different systems like vacuum to fill a shock, we discovered that synthetic oils actually had more air in them, and the reason is because of how their manufactured. Synthetic oil does not have air in it to start, but it is introduced into it during the manufacturing process, mineral oil on the other hand does have air and its manufacturing process is much more precise so it doesn’t introduce more air into the oil. When NASCAR came out and made water illegal to use as an oil for shocks this made engineers go to work and developed a better oil. It was at this time we realized how much air was in the oil and how that affected the shocks performance. It was also the time when oil engineers developed thinner and thinner oils, now we use oils with less than one weight in them. As you know thinner oil allows the shock to make smaller moves or faster movements and returns this back to the driver in the form of better feel. Shock oil is like any other oil the more you change it the better it performs, in most cases we don’t abuse the oil to a point that it needs to be changed but we have introduced air into the oil to a point where it doesn't make good feel for the driver. By changing the oil on a regular basis it helps the driver to maintain better feel and better performance in the car.