Author Topic: Best petrol for a Prius  (Read 7511 times)

happy

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Best petrol for a Prius
« on: October 24, 2013, 05:17:52 AM »
The teenager wrote off my gas guzzling SUV recently so I've just replaced it with a 2009 ZW30 Prius (yes I know it should have been older to be mustachian...but thats what I could get reasonably quickly since the hire car was eating my $oul).

Fuel consumption is down, way down.... probably only 1/3rd of before. I think I will smile everytime I fill up for nearly half as much, half as often.

I'm not very good at cars, and have found conflicting information about the type of fuel. One Toyota source says 95 octane unleaded, and another says 91 octane  unleaded and  inside the fuel cap it says suitable for 10% ethanol. ( in Australia 10% is always with the 91 octane)

I filled up today with 95, and think that the petrol engine is running a bit smoother and the very slight pynking  up  v steep hills seems to have gone. Not sure what was in there before but since it came with a free tank of fuel I bet it was 91/10%.

Does anyone know whether I should run it on 91octane unleaded with 10% ethanol (cheaper, but some say uses more fuel)  or  just shell out a bit more for the 95?

Matt K

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Re: Best petrol for a Prius
« Reply #1 on: October 24, 2013, 08:55:16 AM »
Firstly, Australia and Europe use a different definition for Octane than North America, so be careful of some of the responses you may get on a US centric site like this. Your 91 is not our 91.

Next, go with what it says in your owners manual or on the sticker inside the fuel filler area. Internet experts do not know more than the engineers who designed your car.

Higher Octane is not always better. Most people misunderstand what an Octane rating is. Higher Octane is NOT cleaner burning or more powerful. Higher octane means that it is less susceptible to pre-ignition. In a car that compresses the fuel-air before injecting it into the cylinder (turbo or supercharged) this is very important - it stops the fuel from combusting outside of your engine block. In old cars with worn engines, high octane is useful because it prevents detonating the fuel in the cylinder but before the optimal time (when a cylinder detonantes before the right time it pushes the cylinder the wrong way and produces "knock", which you can feel and hear in the car).

Generally speaking the more 'tuned' an engine, the higher the need for a high octane petrol.

Low Octane has an advantage, it ignites easier, and as long as it isn't igniting too early, this is good for you. It means it will burn more completely, so you'll get more out of the gas than a higher octane. That is why car companies always recommend using the LOWEST octane the car is designed for.

Higher octane petrols are thought of as cleaner because they tend to have more cleaning agents included in them. There are two reasons for this: one, since they may not always burn as clean, more cleaning agents are wanted; two it allows the petrol companies to justify the higher price and sell to more people.

Each petrol company puts in its own additives. And each engine is designed for certain burn characteristics. This means your car may in fact run better on Company X's 95 than company Y's 91 octane. But it may run best of all on Company Z's 91 octane. My old Mazda 6 did not run smoothly on ethanol. It ran best on pure petrol (10% ethanol being the standard here now). My car before that had a very old and dirty engine and ran best on a high octane high ethanol blend.

Ethanol has less energy in it than petrol. So a 10% blend will have less energy than a pure petrol. But ethanol has other advantages, it lowers the freezing point of the fuel, and it is a very stronger cleaner (will help clean your fuel lines and injectors). If your goal is purely fuel economy, on a new engine you'll probably see a few percentage points better fuel economy with pure petrol (I got 5%-10% with my Mazda, but it was an outlier). And if you have an old engine, you may find that the benefits of ethanol outweight the loss of energy content (I got 2%-5% better with ethanol on my Acclaim that had 220,00kms on the clock).

Track you mileage (I recommend a tool like Fuelly.com) and try different petrol stations. Eventually you'll find what works best for your car.

Matt K

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Octane Ratings
« Reply #2 on: October 24, 2013, 09:08:35 AM »
http://en.wikipedia.org/wiki/Octane_rating

Australia uses the RON system of Octane Ratings, US/Canada use AKI. 91 RON in Oz is 87 AKI in NA.

According to the above wikipedia article, petrol from the same station has the same cleaning agents regardless of blend (high ro low octane). Here in Canada, they clearly advertise on the pumps that the higher octanes have more cleaning agents. So, make of that what you will.

Bruised_Pepper

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Re: Best petrol for a Prius
« Reply #3 on: October 24, 2013, 09:14:03 AM »
Wow.  Perfect answer, Matt.  I always hate how people assume higher octane = higher performance.  I guess I shouldn't get mad: I'm not the one overpaying for gas. 

happy

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Re: Best petrol for a Prius
« Reply #4 on: October 24, 2013, 04:23:56 PM »
Brilliant reply thanks Matt. I didn't realise there was an intercontinental  difference in octane ratings so thanks for pointing it out.

When I referred to "pynking" - thats the same as knocking.

So the manual inside the car and the label on the fuel tank indicate 91 plus 10% ethanol is ok. Toyota website said 95. Haha I did the exact opposite of what you said...assumed the more expensive 95 petrol  would be better. So I will gladly go back to 91/10 since its 20c a litre cheaper and maximise my fuel savings.

I have to say in my old car I always used 91/10 since I could not tell any difference in performance or fuel economy between that and 95 or 98.

I usually fill up with the one brand of petrol since it belongs to my discount points system and I get a good discount.

Anatidae V

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Re: Best petrol for a Prius
« Reply #5 on: October 25, 2013, 02:01:22 AM »
I am in fact looking purchasing a '09 Prius, since my partner said nothing older than 5 years. Is it nice to drive? I'm used to a manual and like the control, and I understand these are basically automatics? Also, what do you think is a reasonable price for one, and how do you get them serviced? Can a normal mechanic do it, or do you pay a premium for a particular kind of mechanic? Sorry if these seem like stupid questions.

happy

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Re: Best petrol for a Prius
« Reply #6 on: October 25, 2013, 05:06:24 AM »
Well I'm not a car person at all, and some of my habits are not mustachian as yet with regard to cars but at the risk of getting face punches here is my experience so far. My last car was a Kluger 3.3l SUV (Highlander I think in US) but I am used to driving a variety of small automatic vehicles at work (corollas, focuses, i 30s etc)

It is an automatic with a continuous shift flywheel.  It has a handy brake gear which brakes the engine, useful for going down steep hills and slowing down...saves on the brakes and charges the battery at the same time.

Do I like it? Yes! its interesting and quirky. Its really designed for optimising fuel consumption and on the eco setting actually the accelerator and controls reduce rapid acceleration. If you put it in power mode (adding in more engine than battery)  its more like a regular car. Its not really nippy, but if you put your foot down its perfectly adequate. In fact I wouldn't buy the older vehicle with 1.5l engine, stick to the 1.8L which is the third gen starting in 2009. (ZW30). I'm an optimiser, and love seeing that I'm using battery not engine, and if you are into hypermiling its at its best. Call me a nut, but I'm having fun trying to avoid going into power mode.

I really would suggest you test drive one...it does feel  a bit different to all-petrol cars.  I could imagine a manual driving petrol head may not like it. ( not suggesting thats you...just sayin' it is a bit different)

Due to its aerodynamic styling the ground clearance is quite low, and I am still learning to avoid scraping the bottom. Good car for sealed roads, but it won't handle dips and uneven ground. It feels like a bigger car than it is: a wheel at each corner and its quite roomy inside.

Look at Redbook online for prices- it will give you private sales vs trade-in vs dealer prices. There are two models ordinary and i-tech which contains extra gizmos. I found the Redbook prices a reasonable guide around my way.

I have found a Toyota dealership who does a good job with servicing at a good price, and my vehicle is under warranty. The fixed price servicing is quite a bit less than my AWD Kluger.   I don't know if a regular mechanic can service it: I would imagine it depends on the mechanic. My local options for mechanics are a bit limited and not very  satisfactory from past experience, so I am happier with the dealership, who is pretty competitive with pricing and does a good job.






Anatidae V

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Re: Best petrol for a Prius
« Reply #7 on: October 25, 2013, 05:51:49 AM »
Ah that's good information. We're looking to upgrade our '99 Toyota corolla, so I imagine the acceleration will not be a problem. We're going to test one in the next week or so, looking forward to it :)