I had emailed Havoline technical looking for the HT/HS rating for 5w30 synthetic oil. The responder was very vague in his answer so I queried him again, he still decided to be vague. So I called Havoline and the operator gave me another number to call(oh well I thought) But Sam was a very helpful guy and looked up the product and said the HT/HS was 3.1, I also asked him if the base stock was a dino or was this oil a full synthetic. His answer was that it is a full synthetic. I may be trying this on my next fill.