Below is an explanation I recieved from Royal Purple as to why they are not API Certified.

"API SM oils (the most current API service) have reduced anti-wear additives, which are proving that they cannot provide the same level of wear protection that the API SL oils do. The API SM rated oils are designed to extend the life of the exhaust catalyst. The US government (EPA) deemed that oil additives might be a contributing factor in catalysts not working after 5+ years and require that API SM oils have a reduced level of anti-wear additives by 20- 35%.

Royal Purple is API serviced, but we use API SL oils. They have worked extremely well and have not caused any catalytic converter problems being used in both high performance vehicles as well as daily drivers. We've decided not to move "up" to an SM rating until we can guarantee the same outstanding wear protection, performance and the ability to extend the drains of the API SL version we currently make. Royal Purple Motor Oils have not had a single catalyst plug or stop working, even using our XPR racing oils in streetcars with over 150,000 miles.

We are offering a corporate warranty to you if you choose to use our SL oil in a car requiring the use of an SM oil and your dealer refuses your warranty on any oil related failures due to the use of our oils."

 

Sounds pretty confident, but i go by personal experience and have been very happy with RP so far in all 3 of my cars so far, and can always tell the differnce between it and Mobile1

 

thats good to hear. since walmart has started regularly stocking royal purple around here, i think i might swap to them from mobil 1. in 2 other cars i had, i noticed good performance gains with no wear on bearings/cylinder walls. what filter do they recommend?

 

Search a little more, RP may not be the best for our cars. I am personally sold on Amsoil, that's all I use in my vehicles. Currently using Wix filters but will probably switch to Amsoil there as well (though Wix are excellent).

https://g35driver.com/forums/engine-...out-there.html

 

By the way, before I got my G sedan I used to have a 00 Toyota Celica that I used RP in and a year into using RP my catalytic converter did actually go bad and require replacement. But I never had thought that RP oil would have been a factor until I read the email from RP Technical Support.

 

Interesting input guys, keep it coming i rally like amsoil myself but cant get it locally and getting it shipped is a pain and extra $...

 

Also anyone with support or experience please shed light on QuakerState Horsepower 5W30 aka Q. It is recommended by Ferrari so i would guess that it should have weight to the claims of unleashing all the power, but my main concern is protection for the engine

http://www.qpower.com/

I like this oil in my TL and am planning to switch the G to this as well, as it seem spretty good and is about a $1.50 less per quart than RP