Hey there, I have a Yaris that I do my own oil changes on. As many other fellow Toyota owners will see(Australia/New Zealand), in the manual it states that the car can run on many different viscocities. These include 20w-50 15w-40 10w-30 and 5w-30 Although 5w-30 or 10w-30 is the preferred choice. 30 weight oils don't come by very often or are sold at a much higher price.. Instead 5w-40 and 10w-40 is always on special. Would there be any negative impacts of using 10w-40 or 5w-40 instead?