Do oil change places mix old oil into new?
I have a friendly car mechanic whom I occasionally help with his PC problems. He told me that pretty much all oil change places mix old oil into the new. Especially when the price is low, like $19.99, according to him, if the shop uses real new oil, it won't make economic sense because oil plus filter will cost about as much. So according to him, either change the oil by yourself, or bring your own oil to the shop to change. Wondering to what degree he is right.
Actually it's possible that they do mix the old and new oil. If you mix it correctly you will have some oil that's as good as new. I have never caught anyone redhanded, but I am aware of this practise.