Probably because it's a low volume product and they haven't bothered to update the spec sheet, Mobil no longer claims dual ratings on it's HDEO with over 800ppm of phosphorous, they along with Shell and Chevron, when they transitioned to CK-4 either dropped to 800ppm or stopped claiming dual ratings if the oil is over 800ppm, seems like anything claiming dual ratings with over 800ppm was licensed prior to 2019 or so. Although Delo 400 XSP 15W40 which only recently launched is kind of an outlier, although they may attempt to establish a new standard on dual ratings and then just reneged on it and are now going back to the bad practice of dual rating oils with too much phosphorous so long as they don't claim SP.
The Mobil product guide was last updated in 2022, it shows the 1,100PPM of phosphorous for TDT. PDS seems to indicate October, 2020. I'd speculate that this is because this product is part of the Mobil 1 portfolio, which you find at parts stores, Walmart and the like, so it has a consumer presence that makes having the API SN designation worthwhile.
Mobil (Delvac) HDEO's that DO have dual ratings:
- Delvac 1 ESP 5W-40: SN/CK-4
- Delvac 1 ESP 0W-40: SN/CK-4
- Delvac 1 AS 5W-30: SN/CK-4
- Delvac 1 AFE 5W-30: SN/FA-4
- Delvac Extreme: 15W-40: SM/CK-4
- Delvac 1300 Super 10W-30: SP/CK-4
- Delvac 1300 Super 15W-40: SP/CK-4
- Delvac Super FE 10W-30: SN/FA-4
- Delvac MX F2: SL/CI-4 Plus (wow, old specs!)
Mobil (Delvac) HDEO's that DO NOT have dual ratings:
- Delvac Extreme 10W-30: CK-4
- Delvac Extreme FE 10W-30: FA-4
- Delvac HDEO 10W-30: CK-4
- Delvac HDEO 15W-40: CK-4
I think the limits, which I believe we've now established do not apply to xW-40's that claim SN and CK-4, are a separate discussion from why we have seen a lot of the HDEO's dropping the dual rating.
SP appears to be a different situation. I find some of the language a bit vague on how it applies.
This VOA of Delvac 1 ESP 5W-40 is from 2018 product, so probably SN/CK-4, and shows ~1,200ppm phosphorous:
I've been running this in 2 unleaded vehicles. It's dual(spark & compression)rated. OAI flags oxidation when it rises 10%. Product Description link
bobistheoilguy.com
However, this blackstone report, which is from 2019 and SN/CK-4, shows ~1,000ppm phosphorous:
Virgin Oil Analysis just recently completed, CK4 formula purchased a couple months ago. Figured I'd share, an updated VOA from one I saw while lurking last year. On paper, looks decent enough but in the flesh, it's really a nice oil. Actually smells kind of sweet, like candy, and it hushes up...
bobistheoilguy.com