OK I have read again the FAQ about oil. The RP does meet the spec equal to or better than CG-4 or CH-4. The only thing I see is the RP is 15W40 instead of 5W40, but down here in hot Texas weather I can't see where that would really be a problem. So if the RP is really not VW spec 505.01, what brand oil's is the VW spec. Looking in the VW manual is calls out for 505.00 (01/02) and 505.01 for the 05, but also list CG-4 or Ch-4 oil's or better. So I guess the question is, just what the ------- is 505.01 oil?
Thanks
The simple answer - a 505.01 oil (one that is actually tested, certified and approved by Volkswagen Germany) is a considerably better oil than an oil which only meets CG-4, CH-4 or any other non-VW standard (when specifically referring to a Volkswagen Group TDI engine
).
A more detailed answer:
CG-4 and CH-4 are 'generic', 'one size fits all' specifications - from the American Petroleum Institute (API). That means that API oils, being generic, will suitable (when only API specs, and not any other OEM standards are specified) for ALL types of engines, in all types of vehicles - from small displacement high relative power output turbo diesels in small light-weight performance cars - all the way through to massive displacement non-turbo low relative power output engines in say trucks, farm tractors or earth movers.
Furthermore, the "A" bit of the API - 'American' - nowadays, API are generally targeted towards engines of North American origin (which are generally larger displacement, less technically advanced in design [though I agree that is subjective, and not always true] but with considerably lower power output), and for compliance with North American emissions standards. However, Volkswagen, being European, (and having to comply with differing European Union emissions standards, and also much different types of journies [speeds are generally much higher in Europe, and shorter journies too in Europe]), design their engines quite different to North America. European engines are generally much smaller in displacement, with diesels generally being turbocharged, often rev higher, and will produce much more power than an equivalent displacement North American engine. So with these differences between American and European engine designs, Europe needed to create their own oil standards (initially CCMC, now ACEA), and even following these European oil standards, individual manufacturers felt the need to create their own 'OEM' standards (VW, BMW, Mercedes-Benz, Vauxhall/Opel [GM Europe marques] and even Ford Europe).
So, understanding the above - you should hopefully agree that a 505.01 oil is considerably better 'tailored' to your VW engine. Think of a 'made to measure' suit compared to a suit from a high street retailer - the made to measure on will (should!) fit much better, be made from higher quality cloth, and hopefully last much longer than an 'off the peg' high street suit.
HTH
