Determining mileage for oil change

The engine does not turn all the time. The Prius uses one of its two electric motors to spin the gas engine to high speed before it gives it any gas. This results in a smooth start that you might not notice.

The oil change interval was set at 5,000 miles for your Gen II and 10,000 miles for the Gen III by Toyota. Does it need to be changed at that point? Who knows. But, it keeps your dealer in business. So I suggest you follow the 5,000 mile schedule.

 

Your ICE doesn't have a traditional starter motor, so it's a lot more quiet when it kicks in.
As far as the oil change interval goes....
Your manual says 10k.
I'm pretty sure that the folks who SWAGGED that number out know about the ICE being shut down at times during that 10K.
And yet......
People (like me) will universally disregard the sage (?) council of the people who designed and built the engine and do something different for a dizzying number of reasons ranging from sloth to tradition to frugality to just plain arrogance.....or.....they'll listen to idiots who "know better" than everybody does how often oil should be replaced in an ICE.
Oh yeah....that reminds me.
I change every 5K....and no.
I don't need any oil "expert" validating or disputing my maintenance practices.

This isn't emerging technology.
Today's oils and motors are a lot more advanced, but I've been hearing this same old argument for a while now......and you know the funny part???
That's right.
People who bang the drum the loudest for each of several sides in this argument are usually the ones who trade out their cars every 3-4 years with less than 150,000 miles......and even today's crappiest engines will pretty much do that even if you skip a regularly prescribed oil change or two, and you use WalMart oil and No-Name filters.

There are people who INSIST that you shouldn't go over 5K....or even 3K between oil changes. There are people who (over)spend on special designer fluids that will allow them to circumnavigate the planet without changing their oil (yes....I already know about the oceans.....or didn't you see my avatar? )
Presuming that each of the oil warriors do it like they say they do, then you should see a disproportionate number of engines going TANGO-UNIFORM (look it up) for one group over another....and you know what?
You won't.
That's because they don't.

Want proof?
Go down to your Toyota dealership and ask them how many engines they stock on their shelves...or how many they replace every week.
The answer will probably be close to zero...just like down at the GM....or Kia....or even the VeeDubbaya dealers.
Now.......go to Ebay and search for Prius Engine.
Yup....there are a butt-ton of them. That's partially because Priuses are always getting squashed on the roads, but also because engines generally outlast the car that they're installed in.

Engines just don't break that often when the filters and fluids are changed at something close to their OEM maintenance schedule and with something close to those recommended by the folks who wrote the manuals.

So....
The correct answer????
Is going to be the subject for more "oil wars."

I'd do it the way YOU WANT to.
Good Luck!

 

The engine does not run all the time, and when it doe start it is not started by a conventional starter motor, but by MG1 built into the transmission.
Oil change interval is still calculated on miles driven, but from then on it gets complicated.
Using full synthetic oil the Toyota interval oil change in the UK and Europe for all Prius has always been 10,000 miles or one year whichever comes first. This interval is now standard in the US for the gen3 Prius. Many in the US use this interval for the gen2 "using synthetic" while others stick with the original 5,000 miles irrespective of which oil they are using.
This is further complicated with the introduction of the Toyota Auris that uses the same basic engine as the gen2 Prius where the Toyota interval is now 10,000 miles.
In my opinion none of these intervals are wrong, "using synthetic oil" but using "dino" oil 5,000 miles I believe is the limit. However changing synthetic oil at 5,000 miles I believe is wasting good oil.

John (Britprius)