Oil

Go ahead, might loose a couple mpg but others have had good results with oil burners

 

Or 5W30? Maybe easier to find, was the 2nd oil spec.

 

Australian manuals show this:


10W/30 is what my TOYOTA dealer's invoice shows they use.

 

This is TOYOTA's recommendation in the manual with your car - it's your choice once a car is out of warranty - you could ring TOYOTA and ask their opinion.

 

Or before? Toyota recommends a viscosity, but it's not a strong caution. Doubly so considering your Australian Manual with it's gamut of grades, even though they still recommend 0W20.

The last line you quoted, talks about moving up to higher numbers under certain conditions.

For all my talk, I'm Mr OW20 so far, lol.

 

Won't hurt.
Won't help.

The oil temp in your engine is the same in summer months when it's over 90 in Jawga as it is when it's under 32 during the winter months.......probably somewhere around 190-degrees.
Engine temps are critical in judging whether or not your coolant temperatures are within proper ranges which is why the temperature gauge in a Prius is as big as it isn't.
If you will notice the arrow in the picture above, it extends beyond 80-degrees.
If 90....or 100....or 110 represented a problem with the oil I'm thinking that there'd be a vertical stop with a message saying:
"Hold up there! t's getting HOT!! Better club up to a 0w30 or 40!"

There isn't...

Despite claims that global warming is going to kill off the human race - I do not think it's ever going to get over 190-degrees in the largest state east of the Mississippi....or in Death Valley....or the Gobi desert, or anywhere else you think that you need to run thicker oil.
If you have a 3-4 year old car and you don't check your oil level as often as the manual suggests, you might experience greater oil use after 100,000 miles - but for properly maintained cars in North America, I'd say that there's not going to be much of a difference by going up or down one grade.

As always.....

YMMV

 

I have similar temps here and use 0w-40 and get oil pressure of 30-50 psi. Can't imagine using 0w-20 but nobody has actual pressure readings w it to show what they get. If u used 15w-50 and started up in 40 degree weather the pressure goes high enough to rupture the pressure sending unit

Anyone know if the pump has a hi/lol pressure autoswitch?

 

If it were any other car, I'd say your concern may have merit. I've been around cars long enough to see that Toyotas when run by the specs often have engines that outlast all other brands. I've seen that both up North, and in an area farther South than you are - third-hand to sixth-hand Toyotas barely maintained by people who would not buy synthetic oils, let alone change the oil regularly. It's why I made the switch this time.

My take is that oil quality goes farther to protect the engines than does viscosity these days (when talking about a change of 10 up or down). It's when someone uses a lower grade oil, something closer to dino-oil of days gone past, where viscosity meant a measurable amount more than did the quality. The best synthetics out there both out-flow (in cold weather) and out-perform (in wear) their direct synthetic competitors for the same viscosities.

 

Toyota is well aware they sell cars in hot climates. 0w20 is just fine. These engines have much tighter bearing tolerances than the old garbage American style engines most people learned on.

 

Just out of curiosity, how many miles does the Prius have on it, and how many have you put on it? Just curious because if things have been working, why change now. And FWIW, does anyone else notice that strange word "must" in the statements in the manual regarding oil weights? The oil does a lot more in modern engines than just lubricate the moving parts, and what has been working for those with Gen 3's may not work for Gen 4's.

 

which are the best synthetics in your opinion? i've always driven beaters before but i want to baby my prius : )

 

In the US there is no legal definition of Synthetic.

So as long as the “synthetic “ oil meets the spec and is changed often <5000 miles you should get good wear numbers.

The type of oil is less critical than the change interval, again so long as it meets the spec.

That said the best synthetics tend to be the Euro rated 0w40 which have the most synthetic, best add pack, and the highest TBN. Close second is Mobil 1 ESP

Unless your PRII specs 5w30 or is an oil drinker Euro oil 0w40 isn’t needed for a long life

This place is a good one to talk oil.
https://bobistheoilguy.com/forums/

 

what spec is that? how do i determine if a particular brand of "synthetic" oil meets this spec?

 

You're worried about meeting specs when the dealerships aren't. Buy quality and be done with it.

I've now worked for four dealerships (never a Toyota, but yes to Honda), and most places use bulk oil that they'd rather not name.

This prior Toyota tech knows:

 

Your owners manual and even oil cap list
SN Synthetic in 0w20 or 0w16
(depending on year and region)

Each year may vary slightly but the manual is king.

So open up your manual
the spec can be any number of things including a Toyota spec
But Usually Ilsac, SN, SN+ or SP Is the spec
0w20 or 0w16 is the weight/grade.

So any synthetic on the shelf at the correct weight will work. (Most exceed gf5)

Modern synthetic graded oils from a large national chain (that aren’t from a dollar store or gas station convenience store) all meet the spec for a gasoline car.
Believe it or not Mobil 1 from Walmart works great even though it’s not the greatest, extra most bestest boutique oil
wear and tear won’t be measurably different even though it’s less expensive.

Like I said if you want to get into the weeds go to bobistheoilguy.com

But these days all major brand synthetic oils meet the spec and it’s not hard to verify

 

My philosophy is if it ain't broke don't fix it. Toyota engineers know their stuff and a ton of Yotas out there still plugging away at 300,000 miles using the oil viscosity printed on the fill cap.

The best thing we can do for our cars is regular maintenance with the best being engine oil changes.

 

Very Well Said!

 

VERY WELL SAID!!!!