I've seen a lot of avocation for the usual oil weights and blah blah blah. 

 

Has anyone used HD40 during the summer in your wheeler EA's?

I'm liking the idea, we run steady high rpm's, idle for long periods of time, and don't shut the vehicles down. Everything the oil is designed for.

 

SAE40 is on the recommended weight list from Subaru by the way, for above 60F.

This subject has been covered dozens of times. The general consensus is that the EA series really don't care what kind of oil you put in them as long as it's above 30 weight. HD 40 would work fine. But so would just about any other 40 weight oil. I use 10w 40 royal purple, but that's just cause I find it more cost effective since I can extend my oil changes.