Our 2018 Clarity is ready to turn over 20,000 miles. The first oil change was around 10,000 miles, and was free at the dealer. I have already bought the requisite oil and filter to do the next one myself. But when? Oil changes every 10,000 miles has worked fine on our 2005 Element over about 20 such changes. 10,000 miles is a nice round number, and fresh oil and filter makes for cheap insurance. But it also seems wasteful. I figure that only 30% to 40% of our miles are with the engine running. So, changing oil at 10,000 miles means the engine has only been in use for 3,000 or 4,000 miles. Given modern synthetic oil and the fairly light loading of our little Atkinson Cycle engines, it would seem to make oil changes this frequent totally unnecessary both from a financial and ecological perspective. Leaving possible warranty issues out of the picture, how many here might defend letting the oil run 15,000 or even 20,000 miles, keeping in mind that even 20,000 miles would equate to about 8,000 miles of the engine running in our use case. Thought?