Castrol 0w40 HTHS?

Sep 23, 2014
Anyone know what the HTHS of Castrol 0w40 is? 3.5 is listed, but read that wasn't accurate. Thanks
It's not listed per se but the specs it carries dictates it having it, so yes but indirectly.
oil specs cotinue to get harder to find, although manufacturers have them from required testing for classifying, they want to rely on marketing bull!!
It’s not going to be significantly greater than 3.5, and the repeatability and reproducibility of the ASTM procedure can vary the result about 0.1 to 0.2. Solarent discussed that once on here. If you’re trying to fine-tune your HT/HS by 0.2 then I’d suggest using a higher grade or an oil that reports a higher value.
The minimum required HTHS to meet the API spec for a 0W, 5W, or 10W40 is 3.5. For a 15W40 and thicker, it is 3.7.

If you're looking for a 0W40 with a high HTHS, Mobil Delvac 1 ESP 0W40 has an HTHS of 4.1. It's a dual use gasoline/diesel oil with an SN rating. If it's for a GDI engine, an oil with an SP rating might be more appropriate though.