The owners Manuel says to use 87 octane. I've been using 86?

Hello,

You want to use the grade the owner's manual recommends.
Using incorrect octane for a long period of time can have a negative impact on the engine.
Using 86 instead of 87 may or may not do any damage, however since the recommended grade is 87 you want to use that.

And you want to be careful not to use E85 ethanol. As that can damage your engine systems.

As for where you get fuel it is not as important as long you use one of those well-known companies it will be just fine.

I am curious to know what state you are in. As just about all of the states in the US uses 87 octane as the regular grade.

Please let me know if you have any questions.
Thank you.