My vehicle calls for 5w30, and 10w30 in the right conditions (i.e. summer driving). I found some cheap 10w40 that I posted about from Valvoline and I'm wondering if it would be fine in my vehicle. It's the Hyundai in my sig. Would I need to buy more oil to mix in with it so it takes down the viscosity more? If so I may return it because I won't have much use for it. Can I use full 10w40 in my SUV? Thanks!