Which viscosity grade Synthetic oil do you use, and WHY???...

Maybe I misunderstand, but: "0W-20 is a proven good viscosity for Gen IIs in hot climates" sounds like a recommendation of lower viscosity than 5W-30in a hotter climate?

 

You understood what I wrote instead of what I meant. I meant to say "0W-20 is a proven good viscosity for Gen IIIs in hot climates."

 

I'm a little confused here....but I sling wires for a living. I'm nobody's idea of a mechanic.
The Prius (all variants) have ICEs that are liquid cooled, and thermostat controlled. They have fans too, for when the coolant needs a little help in the radiator with the heat exchange thing.
OK.....so if the cooling system on the ICE maintains a temperature somewhere between 190-200 degrees (I guess---there's no coolant temp gauge in mine!) then why is climate such a big concern? Last summer when it was 100-degrees (+) my fan kicked on and off. It was waaaaay more off than on.
Let's say the coolant system is designed to keep the ICE at 195-degrees (F) just to pick a number.
Wouldn't the oil temp for a Prius in the deserts of Arizona be pretty close to the same Prius if it were driven in North Dakota????
I mean it gets HOT in AZ, but not that hot-----DOES IT, or am I missing something????

It seems to me that if the folks at the Aichi Iron works say 0W-20 is OK---why would it not be OK for an engine (especially one at normal operating temperature) in 'warmer' climates???? I’m digging the fact that 0W-youpickthenumber would be what you would want in colder climes---but they already recommend this.

Maybe one of you "lubeologists" would care to enlighten me????

 

On engines without an oil cooler, and over simplifying a bit. There are four major inputs to engine oil temperature. Coolant temperature, engine power output, engine speed and oil pan cooling, not necessarily in that order.

On my present other car, oil temperature runs about 20F above coolant temperature just cruising down the highway on a warm day and about 80F running it hard on a track. I don't run mine that hard, but others do.

I have read that engine oil temperature tends to increase about 1/3 to 1/2 degree for every 1 degree increase in ambient. I have never tried to verify those number but have seen the trend and oil temperature-coolant temperature spread increases during warm weather and decreases during cooler weather and oil probably runs below coolant temperature at some cold air temperature because of air blowing over the oil pan.

Assuming the 1/2 to 1/3 degree per degree is right, 30 degrees air temperature increase will result in 10 to 15 degrees oil temperature increase. If you look at some oil viscosity vs temperature graphs, 10 to 15 degrees F oil temperature change changes the viscosity of engine oil about the same as one full SAE grade. i.e. 222-227F 30 weight is about the same actual viscosity as 212F 20 weight.

 

One other thing to add to what XS650 has already said.

Just because 0w20 or 5w20 is recommended for cold climates is no reason to assume that it is the optimal viscosity for a warm engine, even for a warm engine being driven hard in a cold climate. It is however reasonable to assume that if it's recommended then it's a good/best compromise between cold temperature viscosity, hot/running temperature viscosity, and in some instances, cost and availability.

 

thats when an engine like the atckin cycle need's the oil up there fast

 

In a hotter climate the oil is already warmer, and therefore already less viscous. You don't need (or want) to use something even less viscous. Toyota's design engineers probably have a pretty good handle on which oil to use.

 

In Europe the recommended grade of oil for the Gen2 Prius changed in 2008 from 5w30 to 0w20 according to the handbooks supplied with the car. If you order a handbook for a 2005 car you get the handbook that recommends 0w20 not 5w30. The 0w20 is quoted as being the oil of preference.

Surely this is because around 2008 0w20 oil became available and was seen as a better choice by Toyota for the Prius and many more of Toyota's engines, even though the mechanical specifications of those engines have not changed. Products evolve and improve and manufacturers move to the later "better" products.

 

Can we get a Toyota tech rep to advise if the USA Gen-2 manual 5w-30 has been superceded?
We seem to have a reached an impasse here on PriusChat.

I go with 5w-30 or 0w-30 on the subjective thought that fuel contamination gives us the visc. lowering we are looking for. Also our Gen-II vehicles are not getting any younger WRT oil losses.

 

Fuel contamination in the Prius under normal conditions should be minimal to non existent with the closed loop emissions system. The only time this may be of concern is a vehicle that only ever does 1 to 2 mile cold start runs that does not allow excess fuel used for cold starts to be evaporated off.

I am not saying 5w30 or 0w30 oils will damage the engine, and if that's what your comfortable with fine. What I am saying is that things move on, and products improve. Who knows what we will be using in 5 or 10 years time.

I agree it does seem strange that different countries with not too dissimilar climates "apart from the very cold" do not get the same recommendation on oil grades.

What oil is required in the Prius C same engine as the gen2 Prius?

 

Just checked on the C forum and guess what, the recommended oil is 0w20 for the same complete power plant as the gen2 Prius.

 

Toyota recommends 5W30 for the Gen II - so I'd stick to that. I was running Kendall Synth Blend - 7500 miles between changes (mostly steady 50MPH on highway during commute hours, no hills) and the oil would be starting to discolor around that time - but recently switch to Pennzoil Platinum to try and extend to 10K. Why Pennzoil ? It was on sale ! For normal use I think any synthetic brand will be fine. If you are paranoid, could do used oil analysis at change to see state of the oil. I would only consider a different grade of oil if living in climate extreme, towing or lots of hills, high speed driving etc. Possible mileage improvement by going to 0W20 has to be traded off for engine wear - esp if engine not designed for that - not worth it to me ...

 

Our 2009 is spec'd for 5w-30. I have been using the PYB (Pennzoil Yellow Bottle) up until now (30k mi). I have switched to Mobil 1 0w-30. I use Mobil 1 0w-20 in the C.

I would recommend 0w-30 in the flavor of your choice. Why? It's synthetic, it's easy to find, easy to remember, reasonably priced, perhaps better mpg (at least not worse), and probably a more reasonable choice for your car than a 20w or a 40w in your climate.

 

I have been using 0W30 in my Gen2 but will probably use 0W20 for my next change. There is only a 2.2 cSt viscosity difference @ 100C. That's pretty close to nothing!

 

I sure wish Toyota USA would approve that chart.

 

I'd rather fight than swtich.
I am sticking with 5W-30 and 0W-30 no matter what anyone says.

Hey side point:
Did you notice with the new website fonts its a little harder to write Mobil-1 5W-30 clearly?
Mobil-1 5W-30 is much more clear (Arial font).
1234567890 <--- ??? 120345968
1234567890

 

We do not know if it's bad enough that your car engine designers in the weather and driving conditions in our individual use. If we did, then we have the best advice on the viscosity than the same size Fits All owners manual to be used.

 

5W30 Penzoil Plat Ultra right now - it was on sale .....
I would only go to 0W20 if I was in cold climate ....

 

0w20. Amsol oil only and filter that is modded I change oil once a year