After watching both amsoil and schaeffer get tested on a lubricity tester machine I gotta vote for Schaeffer.
What's a lubricity tester?
It isn't one of those unapproved machines that many call a one-armed bandit?
Does this lubricity tester check for viscosity, ability of the oil to resist shearing, oxidation, foaming, & so on?
If an oil exceeds in one area, but does poorer (or worse yet fails) than other oils in other test criteria is it still a good oil?
AMSOIL has some good white papers on their website where they test their gear, engine & motor cycle oils against some of the competition. Worth the read even if you just want to understand better the criteria that an oil has to meet.
What makes it interesting is that they name names... and to date have not been sued or have had to stop publishing the results.
Now, some people like to try to discredit or downplay these papers because their beloved brand-X oil wasn't tested... so their argument is that it must be as good or more likely better than amsoil because it wasn't mentioned... If brand-X is so good why don't they publish their own test results showing how much better than amsoil, or mobil, or rotella, or mazolla their own product is?
It is so easy for brand-X to publish test results showing that they beat brand-A & brand-B.... name names if your product is that good.
Anyway... having said that... I agree with earlier comments... if you aren't going to use the benefit of extended drain intervals, any synthetic is going to be costly.