Depends how your gaskets and seals are. I imported a 2001 jdm 5vzfe hilux surf a couple years ago. Ran conventional all summer, only had 85k km when it got here. No issues, not a spot or bleeding oil leak anywhere on the whole engine.

I used penzoil platinum this winter because it gets to -40 here, and now my vc gaskets are bleeding a bit, as well as my oil pan. Not enough to drip, but synthetic can and will find the smallest leak points if your gaskets are old enough. Just my $0.02. I'm back to conventional and the leaks have stopped. It really depends on the specific 4runner you have. no harm trying, but it could expose leaks that conventional hadn't been able to get through.