How often should I be changing the oil of my Prius?

It's implied in the 0W-20 spec. I've yet to see a 0W-20 that wasn't at least a group III base.

I suppose we could split hairs on the definition of what is a synthetic or not, but it's widely accepted (and backed up by a courtroom win) the group 3 oils are considered synthetic. I personally want something more along the lines of Group 4-5 but the group 3s have been proven to perform just fine under "normal" conditions.

 

I do every 5000 miles. can't go wrong. I let the dealer do the 10000 miles and up it after at 5000.

 

So we been recommending the wrong oil weight? There are multiple photos of 0w-16 oil uploaded.

 

I was just at the dealer this morning and asked about this - I had been doing full synthetic every 7k miles or so, but they said that technically every 10k is fine. Interestingly though I believe my car's "maintenance required" warning goes off every 5k...

 

The industry has made better oils which will last longer without breaking down.

They have also, for the sake of fuel economy, went to lower expansion pressure (or tension) oil control rings to reduce frictional loss.

Oil has detergents and additives that keep debris in suspension. Much of the debris is abrasive and "gummy." This combination causes greater wear and "sticking" and clogging of the piston's oil control rings.

The "blow by" past the oil rings into the combustion chamber results in carbon build up and "oil burning" through the exhaust which can destroy the catalytic converter.

Any manufacturer mandating a 3.000 mile oil change would be subject to criticism from competitors. Yet, that would be the best for the life of the engine.

Cleaner oil leads to lower wear and carbon build-up in the engine. I will change oil in my own car at 3-5k miles or every 6 months, whichever comes first.