Do only use only the oils sold by whoever made U car.?
just use the correct weight of oil for the condition's U in.

Do a search and U'll have plenty to read..

BtW I switched to Mobil 1 V-twin; 20w50/motor and pri. 75-90 in tranny.. and happy with it..

 

HD Syn 3 is a blend of dino oil and synthetics... bid out to the lowest bidder. Any brand name full synthetic with the correct viscosity for your areas mean temperatures is IMO a better choice... here I run 50w in the summer. Any brand Type F only ATF in the primary. Here in the panhandle of Florida any synthetic gear lube usually 75-140 viscosity for the higher temperatures in summer and the lower temperatures in winter is best.

 

Doc, engine oil viscosity is measured using a different scale than gear oil. 10 thru mid 20 weight engine oil is the same "actual" viscosity as 75 weight gear oil. Mid 20 thru mid 30 weight engine oil is the same "actual" viscosity as 80 weight gear oil. Mid 30 thru low 40 weight engine oil is equivalent to the viscosity of 85 gear oil. Low 40 thru 50 engine oil is the equivalent to 90 gear oil. And 60 weight engine oil is equivalent to the 140 weight gear oil. I'm tolf there is some overlap, but that those figures are about as accureate as one can get.

 

OK, HD Syn3 oil is not a "blend". HD oil is a full synthetic processed by the so-called "hydro-cracking" method. (IIRC, the term is hydroisomerization.) That means it is a Group III synthetic oil. A so-called synthetic blend would be a mix of a Group II and a Group III. Group II oils are "conventional" or "dino" oils. Oh, and that lowest bidder is only one company, currently CITGO, aka Venezuela's Chavez Oil Company.