quote:
Originally posted by Bob Woods:
PAO cause seals to shrink, Esters cause seals to swell, with the correct blend synthetic oils will not cause seals to fail. Aircraft turbine engines use ester based oils but they also use specially made seals and gaskets. Typically synthetic automotive oils have 90-98% PAO's with the rest being mineral oils and ester with some additives making up less then 25 by volume. Syn-blends average about 50% PAO's and the rest being mineral and base additive package. For those of you that haven't heard it, PAO IS A PETROLEUM PRODUCT. IT IS MADE FROM HYDROCARBONS. IT IS NOT A PRODUCT OF COOKING OIL RECYCLING.