How long should I wait to change synthetic oil
Thank you for writing in. Synthetic oils do last longer than traditional oils. They do not break down as quickly when kept at high temperatures for prolonged periods of time. This means they provide better protection longer. Typically, synthetic oil manufactures will recommend changing it anywhere between 5,000 and 15,000 miles. I personally would never wait 15,000 miles to change the oil in my daily driver. Here's why...
First, your oil is full of detergents that collect and hold onto debris, carbon build up, and other contaminants inside the engine. Even if the oil doesn't break down, it gets black and contaminated unless the inside of your engine is impeccably clean (which is very likely not the case). The oil is recycled through the engine, and if any of that debris makes it passed the oil filter it will be sent back through.
Secondly, your engine loves fresh oil. You could perform an oil change daily, and you would only be improving performance and longevity. While it may be monetarily and environmentally practical to wait as long as you can, if you want to preserve your engine, you will not push the limits.