Do not use premium fuel on prius!!!

According to Wikipedia "Australia: "regular" unleaded fuel is 91 RON, "premium" unleaded with 95 RON"

that is about same as USA where regular is 87 AKI (approx = 91 RON)

 

Who is neone?

The member I quoted "prius_deep" - we don't have any idea where he is. He's just put "road" as his country - which could be on any continent.

 

'anyone'

 

Isn't Toyota's recommend 0W20 for all conditions? I would trust them, why don't you?

 

because toyota doesn't care how long your engine will last once the warranty is gone /
with 0w-20 the engine will very very likely outlast the warranty, BUT, very likely it will NOT last as long as with 0w-40 /
check this forum out, might give you a better understanding why I prefer a thicker oil /
https://bobistheoilguy.com/forums/

 

toyota only wants mpg's

 

Mixing of regular fual with premium made the fual gaze to stop functioning.(stuck at half a tank & not letting to fill gas)
After drying out the tank completely and fueling its working properly.(gas indicator working)

 

Was that a fuel mix problem, or just yet another Gen2 fuel bladder issue?

 

That makes no sense.

Let me tell you something about non-diesel gas stations: They have two underground tanks and dispense three grades of gas from them: Low, Medium, and High octane. They dispense the Medium octane by mixing the High and Low 50-50.

 

We do not have any reports of Premium fuel being the cause of Gen2 gas tank probs. I once had a Gen2 Prius maintenance manual (not from Toyota) that said Premium could cause hard starting problems, but we never had any reports of that here either.

 

I think Research Octane 91 means 87 octane in America, at least that's what I infer from y 2010 Prius (USA, Prius II) manual.

"Your vehicle must use only unleaded gasoline. Select octane rating 87 (Research Octane Number 91) or higher. Use of unleaded gasoline with an octane rating lower than 87 may result in engine knocking. Persistent knocking can lead to engine damage."

 

Exactly. There are a couple ways of stating an octane number, the "Research Octane Number" R and the "Motor Octane Number" M, where the same stuff will have a higher R number and a lower M number.

Then you have places like the United States, where the number painted on pumps is (R+M)÷2, the average value between R and M. 87 is the (R+M)÷2 value for "regular" in the US, which is what's specified for the Prius.

 

ChapmanF is exactly right, as usual, about (R+M)/2.
I'll add that long ago, before that average rating was posted on pumps or listed in owner's manuals in the US, the only octane number we commonly talked about or advertised was the "R" one. People have been confused about that distinction ever since. especially considering other places still use R-only designation, without identifying it as such.

The reason the confusing average method was decreed in the US is that it correlates more closely with real-world knock tendency than either the "R" or "M" rating alone.

 

NO - I was talking AUSTRALIA where they specifically specified 95.

No idea why Australia does that - the present CAMRY specifies 95 too - but PRIUS Gen 4 is 91 - which is your 87.

Really odd is that CAMRY specifies 95, RAV4, with supposedly the same engine, only needs 91.

 

The 13-1 ratio on the Prius engine does not mean anything since it's an Atkinson cycle not Carnot cycle. In Atkinson cycle the intake valve close is delayed making the mixture not compressed as hard as in Carnot cycle so knock is very unlikely to happen even if you use something like 80 Octane rating.

 

If you compare Toyota to Lexus you will be surprised the same engine on Lexus requires higher octane rating than on Toyota. It's all about the tuning.