Ibotta is similar to a cashback or coupon app. If you meet certain purchase conditions, added the offers and scanned your receipts, then it gives you a rebate back. You can redeem your cashback later for a PayPal credit after meeting a minimum amount or for some gift cards. It works pretty well. Some offers are generic, some are for specific products, some are specific products but not retailer-specific, some are specific products at specific retailers.
Check their current offers: https://ibotta.com/rebates
Motor oil-wise, about 2 years ago I was able to get 4 jugs of Pennzoil Plat 5w30 HM for about $12 for 20 quarts after all rebates. I don't use the app anymore though because my buying habits just don't work well with it.