You are okay.

If you haven't attempted that performance tip where you can reset your timing over what was set at the factory (based on the use of lesser-grade octanes), there will be no harm done.

Plus, I find that when I'm stuck in a rural area for an extended period, sometimes I can't get much better than 87 or so...and I'm NOT puttin in that "gasahol" or whatever them "corn-squeezins" mixture is!

__________________
2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car