What I had heard and read (who knows how reputable the source was) is that conventional oil has larger molecules, while synthetic has significantly smaller molecules.. and as a result your seals will be used to the larger oil molecules. When you then put in synthetic the seals may leak.
I think I'll give her a shot and go to fully synthetic.. feedback much appreciated, thanks!
Its not the size of the molecules...
Conventional oils – the oils most people are familiar with – are refined from crude oil. Refining is a process of physically separating light oil components from heavy ones. Crude oil contains a full range of different kinds of molecules. Many are similar in weight but not in structure. The refining process cannot distinguish such molecules, so a wide assortment of molecules is present in a finished lubricant made from crude oil stocks.
Some crude oil molecules are not beneficial to the lubrication process. For example, paraffin causes refined lubricants to thicken and flow poorly in cold temperatures. Molecules containing sulfur, nitrogen and other elements invite the formation of sludge and other products of lubricant breakdown, especially in high-temperature applications. Sludge and breakdown products significantly increase wear rates. The assorted molecules of refined lubricants also have different shapes, making lubricant surfaces irregular at the molecular level. As lubricant layers flow across one another during the lubrication process, these irregularities create friction, which consumes power, reduces efficiency and increases heat and wear.
Synthetic lubricants are chemically engineered from pure chemicals rather than refined from crude oil. That gives them significant advantages over refined oils.
The base stocks from which synthetic lubricants are made contain no sulfur, nitrogen or other elements that invite the formation of sludge and other products of lubricant breakdown. Synthetic lubricants can be used in higher temperatures than refined lubricants without breaking down. Their resistance to breakdown also allows them to be used longer than refined lubricants can be used. Lubricated systems stay cleaner and last longer with synthetics.
The base stocks from which synthetic lubricants are made feature uniform and smooth molecular structures, which ensures low friction as lubricant layers slide across one another. Reduced friction increases energy through-put for greater fuel efficiency and power, and reduces heat and wear for longer equipment life. Molecular uniformity also helps synthetics resist thinning in heat and thickening in cold, which helps them protect better than refined oils over a system’s operating temperature range and helps ensure secure sealing.
Many different kinds of base stocks may be used to create synthetic lubricants, allowing a synthetic to be designed for virtually any application. Some base stocks are ideal for use in extremely cold environments, others are perfect for use in extreme heat. Some are extremely safe in applications in which refined lubricants pose a fire or explosion hazard. Refined oils simply do not offer the design flexibility synthetics offer. The designability of synthetics also allows them to be tailored very specifically to the needs of everyday applications, such as automotive engines, commercial equipment or industrial machinery. That specificity helps ensure long life and peak power, performance and fuel economy from the lubricated system, as well as long lubricant life.
