Back when I started using Purple, I used it based on the rec from a pilot friend of mine that used it in all of his aircraft engines. Granted it's not published, but the data he was getting back from his FAA mandated oil assays was enough to convince me. To be fair here, I had the oil sludge problem in my 1.8t just over 100,000 miles, having used Purple since 10,000 miles. Since that hefty repair, I have been using Mobil 1. Initially it was an availability issue, I got tired of paying shipping on top of the price of the oil. At this point, I think the performance of both Mobil 1 and Royal Purple are close enough that it no longer justifies the price of Purple. I'm sure both companies could supply plenty of data to say otherwise, JMO.

 

Whoa!! 77 bucks for some oil. no thank you. i use the purple syrup

 

That is $77 CDN for 6 bottles. I think it is still cheaper than Amsoil and a bit higher than Mobil 1.
They claim it is 85% PAO which is the ingredient that Mobil 1 don't claim to be in their mixed.
Never tried Motrlube yet, but with Mobil 1 I am quite happy.

 

If I remember correctly Purple was over $7.00 a quart. I bought it in a 5 gallon bucket last time I ordered it.