Hey everyone, New member to this forum. So I've got a Yaris . Used only a few times a week during the city and engine barely heats up before reaching destination (max 5km). Only travel longer distances (20km~) 5-10 times per year. Annual mileage would be around 4000km per year. I never let the oil go for more than one year. Currently filled with Vavoline 10w-30 Semi-Synthetic. Due to the engine wear this kind of driving entails should I change to only using Full Synthetic? What are you're thoughts on drain intervals and oil type?