I don't think so. Each strand, as small as it can be, carries its load of current and it doesn't matter whether strands are in contact with each other, so long as they total the required gauge and so long as they are all in contact at each end of the strap. They can be covered in slime and will still carry their part. Litz wires, such as those used in inductions heaters and induction cookers are built this way. Each strand is insulated separately and doesn't contact other strands, and the sum of their individual gauges carries enormous amounts of current. Of course the contact points at each end still need to be dead clean with no trace of corrosion.

It will clean up like new if you first clean the grease/oil off with thinners then immerse the strap in pickling vinegar (10%) for a couple of hours.

Thanks for confirming Ed! Since my car has passed through a few hands prior to me owning it, I just wanted to confirm it was in the correct placement! On to other potential areas for possible grounding issues!

Best,
Nick

I don't care if my ground strap is greasy. IMO, it helps prevent corrosion of the strap and at the contact points. You do you.

Totally agree with Wazzz, a dirty ground strap is ok. Be sure it isn’t frayed as that reduces the current flow capacity and is bad. The electrical contacts must be clean. Don’t use dielectric grease on the contact places, use a conductive grease.