Originally Posted by megabyte5689
I've always been told as a good rule of thumb that if you start the vehicle out with a synthetic oil, you stay with the synthetic oil. I've heard way too many stories of leaks showing up after the switch and other problems arising. I just use the 5w30 in mine and change it at the 3,000 mile mark
Even though SoA recommends that you stick with synthetic if you begin using it in the latest Outback owner's manuals, this is 1980's logic. You can contact any of the oil companies and they will tell you this. Oil manufacturers today balance their oils much better than oils only just a few years ago. Now if if have been running conventional in a WRX for 75,000 miles at 6,000 mile intervals, chances are there is a lot of sludge in the engine and around the gaskets and seals. Switching to a synthetic in this case will clean up the sludge and perhaps leak past the seals that were previously blocked with sludge. This is just a case of poor maintenance the first place.
Myth: Mobil 1 will leak out of the seals of older cars.
Mobil 1 does not cause leaks. In fact, new Mobil 1 was tested in dozens of industry standard and original equipment manufacturers (OEMs) tests to prove its seal performance. It is fully compatible with the elastomeric materials from which all automotive seals and gaskets are made. If an older engine is in good condition and does not have oil leaks, Mobil 1 provides the same advantages as when used in a new engine. ExxonMobil recommends taking measures to repair the leaks, then using Mobil 1. ExxonMobil also recommends following the automobile manufacturer's manual for the proper oil to use.