I've read all the posts about people saying Toyota approved 0W-20 oil for their engines. And then read the posts (from Toyota) that informed everyone the Prius engine was not part of this switch.

So much confusion!

Well... so it sounds like what's definitely approved for my 2006 is 0w20 in the transaxle (so that's where the Toyota invention stuff I read came from), and 5w30 in the engine. I live in LA so cold weather... doesn't exist. So I'm in the lucky position of not needing the benefits of 0w20 in the engine. 5w30 it is for me! Thank you everyone, although I'd like to see this discussion continue for those in cold climates (like me in case I take a road trip) - has anyone here used 0w20 in their pre-2007 Prius, for example?

Prius 2006, bought September 14:

Many people has used 0W-20 in their Prius but be warned, if your vehicle is still under warranty and you have an engine oil related malfunction, Toyota will not cover it if they discover you used the wrong oil. Is it worth the chance....no. Remember Zero weight oil only helps on startup, the 20 weight side saves more fuel than 30 weight but not much in my opinion.

I owned a CVT Honda Insight that used 0W-20 oil, the vehicle was lighter, had 3 cylinders and used special LRR tires. My Prius uses 5W-30 oil, has 4 cylinders, is heavier, bigger and uses normal tires yet still gets close to Insight mileage.

Well, I don't want to start a warranty flame war as I've seen elsewhere, but I am curious to know if anyone has had Toyota "discover" their use of 0w20 in the engine, and what the response was.

Prius 2006, bought September 14:

It is not that hard to figure out what weight oil is used, afterall Toyota will do an oil analysis.

Right, not wondering if it's hard to tell, but what responses if any people have gotten from a Toyota Service location.

I'm at Northridge Toyota right now, enjoying a nice ripoff. To get synthetic they're charging me $60 instead of $40. They didn't want to change my oil at 1500mi (as recommended here) because "Toyota's are better cars." I stared at him to let the absurdity set in, then told him I'd like it done anyway.

I'd be fine with the cost but they won't even let me watch them do the oil change. Blah. I don't have a driveway or anything that would be a reasonable location to do this myself... not looking forward to the next change.

Prius 2006, bought September 14:

$60!!!! Heck even $40 is way to much for just an oil change! Find any road anywhere and do your own oil changes. It is easy and saves you so much money.

It is a strange story...
In Japan, my Toyota dealer puts Toyota Genuine Castle 0W-20 oil to my Prius everytime since 2004.
The 0W-20 oil is also listed on the Japanese owners manual as one of recommended oils.

Ken@Japan

Yeah it sounded ridiculous - I realize Synthetic costs a little more but that was stupid.

But I'm not - I'm going to try someplace different next time that my friend goes to and thinks does a good job, for $20 - but that's not synthetic. If the syn price is good it looks like I'll end up there in the future.

Prius 2006, bought September 14:

Yea well not in the U.S., and every memo I have seen about it still says the 0W-20 oil is not approved for the Prius engine.