Panel/cover by oil plug not properly secured by mechanic. Caused severe damage of front tires while driving on the interstate. How can I explain this to the mechanic when trying to explain cause and effect? Had to buy 2 new tires when existing ones were only 5 months old.

 

That is only one of the reasons I only trust the dealer to do my oil changes. I used to do them myself but no longer feel like crawling under my car.
The fourteen 10mm bolts needed to properly secure that fiberboard shroud underneath the vehicle might be too much for the cheapee oil change shops to do a proper job.
At least they put oil in your vehicle.

If you paid by credit card, have the credit card company request a charge-back to you for the total damage caused by improper workmanship.

Telcoman