I did my own oil change the other day. And I drive a Prime mind you. So it maybe rougher or it maybe used less than a regular Prius. All I know is that at 12,000 to 14,000 mile change interval, that oil looked rough. Is it enough to hurt the engine? Probably not. But I think a 7,500 interval is just fine. 10,000 is likely pushing it to the limit and that is for a Plug-in Prime that is dual duty. I use the plug-in feature exclusively for slow speed 35 to 25 to 15 driving. Commercial zones are 15 FYI. And the engine is exclusively used for high speed 45 to 65 driving. Sometimes I touch 70 just to know what it feels like to be alive..... I will probably start doing my own again for 7,500 miles. See how rough the oil looks for myself.
As long as there still enough additives left to do their job of protecting the engine and keeping sludge from forming, doesn't matter too much how the oil looks.
When Prius owners report their oil looked "like new", I suspect they're judging by the film clinging to the dipstick, not something like a jam jar of drained oil. That said, while ours looks dark (viewed by the latter method) after just 2~3K kms use, it's still a lot better looking than the drain from a gasser after say 10~12K kms.
I think hybrid engines are in general very easy on oil & filter. I do DIY change on my RX hybrid. After 12 months / 6000 miles, there is absolutely no metal shavings in the filter and the oil does not look dark at all. If the catch pan is clean I’d not feel bad putting the oil & filter back for a few thousand more miles…
When I had a shop and was still turning a wrench the recommendation was every 3 months or 3K. Of course in those days automobiles required much more routine maintenance. (points, plugs, filter, adjustments and oil changes) I am a firm believer in doing oil analysis. It is the equivalent to a blood work up. I managed several fleets of commercial vehicles and did oil analysis on some. I was able to predict with certainty when an engine was reaching the end of its life. It proved to be very cost effective, in that it reduced down time and unexpected failures. I think it is routine with aircraft maintenance. I owned a 2015 Gen III and did oil analysis with each oil change. (5k, 10k, 20k and so on) I was using Mobil 1 0/20w and I to had more than a little bit of doubt about the recommended oil change interval. I did a complete analysis testing every parameter available. At 10k the oil was still serviceable!
