A few good pionts on synthetic oils they do things better than an average oil. They will reduce wear, resist oxidation, have less volatility, leave fewer deposits, provide a more stable viscosity (thin out less at high temperatures and thicken less at low temperatures), Synthetic oil lasts two to five times longer than conventional oil; thus, waste oil generation can be reduced two to five times if synthetic oil is used. Synthetic oils have high resistance to changes in viscosity due to temperature. As a result, they provide a heavier, more stable protective oil film for engine bearings and piston rings than is provided by similar SAE-grade mineral oils. Synthetic oil permits better performance and longer endurance. synthetic oil yields better fuel economy, reductions in friction and wear, decreased oil consumption, improved performance, and extended drain intervals.Although some synthetic compounds are not compatible with conventional oils, adding a quart of synthetic oil to conventional oil produces a compatible mixture. However, the lower friction resulting from the use of synthetic lubricants makes them unsuitable for break-in.
The synthesized hydrocarbons, polyalphaolefins, diesters and other materials that form the base stocks of high-quality, name-brand synthetics are fully compatible with petroleum oils. In the old days, some companies used ingredients that were not compatible. As a result, manufacturers of quality synthetic lubricants were tarred with the same brush. Fortunately, those days are long gone.
Compatibility is something to keep in mind, however, whether using petroleum oils or synthetics. It is usually best to use the same oil for topping off the oil you have been running in an engine. It is preferable not to mix your oils, because the functions of additives blended for specific characteristics can be offset when oils with different additive packages are put together. For optimal performance, it is better to use the same oil throughout.
