I am approaching the 140K OCI. Have been using Mobil 1 0W-20 Advance Fuel Economy oil since I've owned the car. With concerns of sudden oil consumption without notice on high mileage engines using 0W-20, was wondering if it makes sense to switch to Mobil 1 0W-40 European car formula. It's my understanding that this is the only true synthetic oil available from Mobil. Any thoughts or comments greatly appreciated. Thanks. About my Prius: - 2013 model 4 with 140K miles - Oil changed every 10K miles - The engine does not use any detectable oil - Major DIY service done at 120K. Cleaned all Engine components including the EGR valve and cooler. Replaced PCV and spark plugs.