I stopped using those discount tire places for a reason like that. Mavis Discount Tires here in the North East. Went in for tires, they come out and tell me oil is dirty, air filter needs replacing, blah blah blah. I said, NO, Just The TIRES!
After i left had an engine light on, turned right around and back in they said its nothing they did, they just changed the tires. BS! You obviously went under the hood and touched stuff to tell me the oil was dirty, air filter, etc.! I honestly dont remember what the issue was since its been about 4 years but my mechanic fixed it. But I just don trust "discount" places because they need to make up for the "discount" some other way like telling you all the extra things you should do.