To Change Oil Type or Not? 2005 Prius 128k miles

Synthetic oil theoretically allows 10,000 mile oil change intervals, and there are people on the forum who regularly use synthetic for exactly that reason.

For high-mileage oil, I was just reading this article that explains it: Should You Use High-Mileage Oil in Your Car? » AutoGuide.com News

 

Are you consuming any oil between changes, and I assume you're currently following the US second generation 6 month or 5000 mile oil-and-filter-change interval? If so how much?

 

If you get 20k miles within a year you can try Mobil 1 Annual Protection. There is also Extended Performance which would last 1 year or 15k miles, whichever occurs first.

 

I considered the same thing recently, I'm at 182k burning a quart per 5,000 miles, most of which seems to burns towards the second half of the 5000 miles. I ultimately decided just to keep two quarts of the Walmart 5-w30 ($2 per quart) in my trunk with a funnel and keep her topped off after the 2500 mile mark. If I'm going to burn it, might as well burn the cheap stuff. I'm not sure if a synthetic would burn less, but I'm not having any other engine issues so just staying as-is.