Castrol has a New Synthetic Oil on the Market, it's called the EDGE...15,000 miles or one year between Oil changes.....

I'm a little leary of this one...I still like the 3000 miles or 3 mos better.

 

I don't care how many miles it says on the bottle. Seems when I buy a used car the Gunk Motor Flush I use before the oil change and the Rislone I use after starts breaking up a lot of sludge and using a full synthetic is just a waste of money as I'll need to change it every 3000 (or less) anyways. After a year or two of undoing the harm the poor maintenance of the previous owner did, my oil stays fairly clean for fairly long periods of time, so then it might be worth spending a few extra bucks on the good stuff.

I really wish someone made a DIY kit for oil analysis though. Visual inspection isn't terribly accurate, especially for tranny fluid where dark may actually be better. And the "sniff test" to check if regular motor oil smells "burnt" doesn't work with synthetics. But oh well, at least with engine oil you can't really change it too often. That's not true for tranny oil though.