Walmart offers the Prestone Antifreeze / Coolant Tester, model no. AF-1420, for $2. (Amazon charges the same with free shipping for Prime members, although it's currently on backorder.) Opt for in-store pickup to avoid the $4.97 shipping charge. That's the lowest price we could find by $5. It helps test for antifreeze/anti-boil protection, rust, and sediment.