Do not use premium fuel on prius!!!

wow, I like your conclusion: 'Due to the 13-1 expansion engine ratio, (high compression engine) it started hesitating and having a rough start transition from hybrid to ICE power.'
one keyword here: atkinson cycle/
(& the ice gets revved up to like 800rpm neway before the ignition gets activated)
I wonder where you 'researched' that?

probably a good idea..../

that has nothing to do with the problems you mentioned/

not a good first post to introduce yourself..... just saying/

 

Using high octane fuel should not lead to engine problems. Premium fuel is only more resistant to knock. Engines that do not need premium fuel but that are run with it suffer no adverse effects from that.
Whatever you experienced, it is not due to the premium part of the fuel. The fuel may have been bad, you may have other problems, but the advice not to use premium fuel is bogus.

 

I use premium fuel only from day one, no issues at all, and Toyota states in the manual use 87 or HIGHER.

 

I'd suspect you got a bad batch of fuel, as premium wouldn't cause those symptoms. Or maybe it's due for new plugs or something anyway. I'd talk to TOYOTA before jumping to conclusions.

Gen 3 in Australia, TOYOTA specifies Premium 95 fuel (unless absolutely unobtainable as a temporary solution).

My Gen 4 2016 specifies "Research Octane Number 91 or higher" - 91 being our regular here.

 

I'm going to agree with you...in this specific manner.
I run regular fuel in The Prius because it's recommended- and I can.

A huge benefit with The Prius is not only fuel efficiency, but that you can also run on regular. Why should I throw that benefit away?

That being said? Occasionally. maybe 2-3 times a year, I run a tank of premium, I also will run a treatment of fuel cleaner...Techron.
I don't feel it does any damage, even if any benefits I may be imagining are placebo related.

The Prius can run on regular. So I mostly, nearly exclusively- run regular.
It's ALWAYS cheaper than Premium, and even when I run a tank of Premium, I don't feel any real benefit.

If The Prius required premium fuel that would be different, but the reality is just the opposite.
I'm going to enjoy the great fuel economy AND the economy of being able to fill up on regular.

 

could be you need to disconnect your 12v for a minute, since the ecu was planning on regular.

 

Your mileage won't be anywhere close to what it could be if you use Toyota's recommendation for your conditions.

 

I wouldn't run 0w-20 where you live/
in fact, I run in all my cars 0w-40 (& new mexico is probably most of the time not as hot as south texas)
what sense does it make to get 2mpg more but the engine dies on you way earlier than with using thicker oil?
guess it all depends on what you want..../
better save than sorry/

 

No, this is not a high compression engine at all. The true compression ratio is very ordinary (8.5 to 9?).

The expansion ratio is different because of the Atkinson cycle.

 

Am I old enough to be reading this forum?

 

Actually I bet that is incorrect. I don't have a gen 3 to check the manual but I would bet that it says to use 87 octane, not "regular" because regular varies. Here in Colorado, "Regular" is 85 octane. In Montana "Regular" is 85.5 octane. At lower elevations "regular" is 87 octane. Do you run 85 octane at higher elevations or do you stick with the recommended 87? I've emailed Toyota, Exxon and Shell asking this question, they all say 87, no lower, regardless of altitude. I've only owned Chryslers before but they told me as long as I'm staying in the mountain region 85 is OK. Not sure who to believe but I'm running 87 in it for now. It annoys me because my gas savings isn't as much as I had expected because of it. I would bet that the majority of cars in Colorado are fed 85 octane and apparently without problem.

 

I have not seen a problem with Premium, but my Bentley Publishers Toyota Maintenance Guide (for Gen2 Prius) says Premium can cause harder starting.

 

You've made yourself a Gordian Knot there, fugedabout it, just go for the regular pump. Which I think you're saying anyway.

In Canada the gas rating system don't jive with what's in the manuals, I think that's actually in our constitution, everything we do is like that, lol.

So I just think regular, forget everything else.

 

What's funny to me is that I often run "regular" in my sportbike. A guy who did GP racing told me the high octane really didn't do much unless you need every HP the motor can crank out. For my use (casual touring), he said I'd not see a big improvement for the cost...especially if I ran fuel system cleaner on a regular basis. For all the talk of "octane," chemically it's a very tiny portion of the gasoline molecule/formula.

 

I run premium every winter, soon as they bring out the "winter formula"

 

But what's your rationale?
I can see the potential issue with harder starting of Premium would be less with Winter blend.
In your region, winter blend could have more MPG than Regular, but not in my region (RFG).