I am sometimes amazed at all the angles we can come up with to look at an issue. The OP has a valid point whether he is "right" in his point or not. I was a retail store manager for almost 20 years and there is a good way to handle this that works every time. The customer is always right. You acknowledge that the ad could be misrepresenting your intentions as a supplier and because of that you honor the price on the ad and give the customer the "motorcycle blend" oil. You do it every time someone comes in for motorcycle oil during that promo. Then you contact your ad department and make sure that a distinction is made in all future advertising. How many other people will come in looking for the same deal? I don't know but I assure you they won't go broke going the extra mile for one promotion. If nothing else, I was known for fairness and it served me and my company well. One of my boss's favorite saying about customers was "kill'um with kindness". I know this is a dieing philosophy as witnessed by the, they don't care so move on attitude expressed here. Not saying that sentiment is wrong, just sad.
As I said before not only have I worked for Advance Auto as a Commercial Sales Manager, but Autozone in the same, and other (parts sales manager, inventory crew leader, remodel team leader), capacities. I always made a concerted effort to make the customer feel that they were appreciated - not only my commercial customers who were always being courted by other retailers, but the walk-in customers as well. I didn't always give them everything they wanted, because sometimes what they wanted wouldn't solve their problem, but they always left with good service - and I had some come back in just to thank me for pointing them in the right direction and saving them money.
I went to a different Advance Auto store today, and I brought the ad in with me, and while the store manager advised me that the ad was for the automotive oil only, he did honor the price, and I thanked him for honoring the ad.
