What is synthetic oil? Synthetic oil is made by synthesizing chemical compounds that were not originally present in crude oil. The new base oil is then combined with a series of additives. The main difference lies in the fact that synthetic motor oils are created utilizing a specially "synthesized" base oil where the size of the oil molecules are all of an ideal weight and of a consistent size. While a conventional motor oil is made up of different molecule sizes which are mixed together, along with various waxes and impurities, a fully synthetic oil is made to provide a much purer base oil, with less waxes and with a uniform ideal particle size to help increase the oils viscosity level. The additives which are used in the production of synthetic oils can help to create an extremely stable engine oil which will sustain the correct viscosity levels across a large range of temperatures. So what does synthetic do for you? 1. Superior friction reducing between sliding surfaces. 2. Lowers engine temperatures. Oil accounts for 1/3rd of a rotary's(engine found in mazda's) cooling. You will typically see ~10 F lower temperatures with synthetic due to reduced friction between sliding surfaces. 3. Reduced foaming. Foaming is caused by air bubbles that become trapped in the oil. The bubbles prevent heat from escaping the oil, causing temperatures to rise. 4. Burns cleaner. There is reduced carbon deposits because of the ash less base. Synthetic oil also has less impurities and will burn cleaner than conventional oil. It's all but required for new diesel engines because conventional oil has much higher sulfur content. 5. Synthetic oil lasts longer then conventional oils in extreme heat conditions. This becomes especially important for FI cars. What are the drawbacks to using synthetic oil? 1. Main drawback is cost. Synthetic oil can go for more than twice the cost of conventional oil. 2. Not suitable for breaking in your engine. Synthetic oil's lubrication and additives will inhibit the break in process. Your first few oil changes for your new car should be with standard mineral oil. However after breaking in the engine you should switch to synthetic oil. 3. Oil leaks can occur when switching to a fully synthetic oil with an old engine. The introduction of a synthetic oil may cause the detergents in the synthetic oil to break down and clean-up waxes and sludge which was maintaining the seals in the engine. However, new engines dont have this problem. Decide if you want to use synthetic sooner rather than later. Questions and answers Q: If synthetic oil resists heat better than conventional, doesn't that mean it's not going to burn in the engine as it's injected? A: You're not burning quarts of oil at a time. The MOP is injecting tiny amounts of oil to lubricate the seals. At that ratio of gas to oil, the oil mixes with the fuel and burns quite easily in the 1600+ F temperatures in your Engine. Q: Does "FULL SYNTHETIC" really mean the oil is synthetic? A: No. Oils such as Castrol Syntec say "full synthetic" on the bottle, but are derived from crude oil. In 1997, Castrol changed the formula of its Syntec "full synthetic motor oil" and removed PAO from the base stock. It's now based off of hydrocracked mineral oil. This move saved Castrol's production costs by 50% while they continued to charge normal synthetic prices. Moral of the story: Make sure you do some research before buying. Castrol isn't the only one doing this. Q: How do i know what type of oil is suitable for my car? Normally, it is advisable to check the manual that came with the car. This usually has the recommended prescribed oil. However, if its unclear from the manual. You can always call the dealer and ask. They will tell you what oil is suitable for your car.