quote:
Originally posted by MolaKule:
Not so. All seals will wear, but there is NO correlation between modern synthetic oil usage and leaks.
I have been using various synthetics from various brands since '74 and run in various engines from single cylinder lawn mowers to V8's, and have never seen any leaks from synthetic use.
I have purchased used vehicles in which sludge buildup from dinos have degraded the seals. I had the seals replaced and synthetics installed. No leaks after that.
I found recently that the 2004 Mazda RX-8 Owner's Manual no longer has an admonition against the use of synthetics. That seems to indicate some progress since for a long time Mazda’s warranty was voided if synthetic motor oils were used.
On the other hand, if you were to look at the warranty claims of a large automobile manufacturer, say Daimler-Chrysler, you'd find that synthetics are overrepresented in claims over the last 20 years involving seals and gaskets. You'd also find ester base synthetics more often than other synthetics.
This may represent some sort of sampling issue, where a dealer or service rep only notes synthetic usage because he consciously or unconsciously relates synthetics to seal and gasket problems.
On the other hand, it could represent some failure on the part of small companies to take into account the wide variety of applications, gasket and seal materials, and conditions of use when they formulate a motor oil using synthetic base stocks, particularly esters.
Exxon Mobil, for example, continuously evaluates its production and experimental motor oils in test vehicles. It also tests competitors’ products. In addition it considers field experience in a variety of uses, including stationary equipment, trucks, automobiles, oil heaters, and oddball equipment you didn't even know existed. Its current products represent four decades of experience with about a 2/3 share of the synthetic motor oil market.
A smaller company may not be able to afford that kind of testing. I notice, for example, two of the motor oils on the shelves at a local speed shop, Neo Synthetic and Red Line, are not even API licensees.
I'd be cautious about filling a crankcase on an automobile under warranty full of an exotic mixture, with quirky additive packages, lacking an API or ACEA certification, unless I could afford to replace the engine out-of-pocket.
I'd also be cautious when dealing with former Eastern Bloc vehicles like the Lada, the ZIV, or the Ural motorcycle. Some of their seals and gaskets are comparable to pre-WWII American cars.