Hate to rain on everyones parade but Rotella T6 is not recommended by Shell for gas engines with catalytic converters. I e-mailed their tech dept today and here is their quote:
"Dear Sir,
You should always follow the viscosity recommendations in your owner's manual. Please note that Rotella oils are not recommended for gasoline vehicles with catalytic converters.
Best Regards,
Shell Technical"
I then asked them how this can be since T6 is API SM rated for gas engines. Here's what they said:
"The API SM specification does not address the use of catalytic converters. The ILSAC GF-4 / GF-5 specifications restrict the use of certain anti-wear additive systems. These can shorten the life of the converter as the car ages and begins to use oil. Because of the higher levels of the ZDDP additives in Rotella oils, they do not meet the ILSAC specifications and cannot be recommended for use in vehicles with catalytic converters.
Regards,
Shell Technical"
My put on all this: that while T6 meets SM requirements, it does so with no reference to also being cat safe. To improve cat life, some ILSAC ratings required manufacturers to lower Phosphorus levels to about 800 ppm or lower because high Phosphorus levels kill cat converters. Since the Phosphorus is contained in ZDDP, meeting this requirement would necessitate Rotella lowering their Phosphorus levels from current levels of about 1100 ppm to 800 ppm or less. Rotella chose not to lower Phosphorous to the required 800 ppm level because higher levels have other benefits to diesel engines, and diesel owners are their main customers. This means T6 does not meet these lower Phosphorus levels and that there are other oils out there that do and these are better for cat longevity.
So...there ya go....it is a great oil but NOT for gas engines with cat converters.
There is one saving grace I can think of: the Phosphorus has to get by the rings to get into the cat converter. If you are not burning oil it MIGHT be ok but I wouldn't risk it. Then again, if you are burning oil of any kind that too can kill a catalytic converter and it doesn't have to be a high Phosphorus level to do it......
So...what are all you gas engine folks who use Rotella T6 going to do? Thoughts??
PS. I rained on my own parade too....the BMW I bought has T6 in it right now.....
so I too have to decide what to do.......