What kind of oil does the 2007 Toyota Yaris take?

Each configuration of the 2007 Toyota Yaris has the same 1.5L 4Cylinder engine under the hood, which requires the usage of the same oil type: You'll need 3.9 quarts of SAE 5W-30 full synthetic oil. In emergency situations, it's also possible to substitute in SAE 5W-40 conventional oil, but this is only a short term solution -- You should never ever run this oil in this engine for the long term. The reason for this is simple: oil viscosity. When You use a thicker oil (higher numbers), it leads to premature engine wear and tear because of the friction and heat created. This, obviously, isn't good -- so if You want to keep Your Yaris running for as long as possible, use the oil with the lowest weight that's recommended by Toyota. In Your case, that's SAE 5W-30.