My friends motor that foamed only saw Mobil 1 synthetic before trying RP... after the foaming he drained the RP, went back to Mobil 1 and never had an issue since.
My tranny on the other hand makes noises @ low speed ever since I put RP in (previously was OEM oil).
Oil is a touchy subject, but the for cost of RP engine oil you're just not getting your moneys worth, especially when people think you need to dump fully synthetic oil @ 5k just because it makes them "feel better".
And like I've said in another thread on here, the only way to tell how good your oil is with your intervals and setup is to get it analyzed.
E36 · DYNO · TUNING · WIRING · PARTS