$/100km. 91 v 95 octane petrol?

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Reply # 755361 4-Feb-2013 09:19

95 RON tuned car with 95 ~ maximum efficiency
95 RON tuned car with 91 ~ less efficiency, increased engine wear and less power, not worth it

91 RON tuned car with 95 ~ a little bit more efficiency/power maybe, not worth it
91 RON tuned car with 91 ~ maximum efficiency

Airfilters and oil are the two primary maintenance requirements in a modern car. Another one which most people forget is the the inflation of tyres. They are reasonsably cheap, and if you have a popular car just wait for Supercheap or repco to have a sale and get a discount on oil and filter, stock them up if that is your kind of thing. I generally went up a grade in oil as well whenever I can, just becareful how quickly you change grades as cars get used to certain grades, but I am running our car on fully synthetic.

Other maintenance can generally be scheduled by observing changes in the way the car drives. Noises when starting stopping and turning (low speed especially) are the ones to look out for. Plus VTNZ are pretty good at pointing out things under the car which you don't generally notice.

Last one to keep in mind is cam belt vs timing chain.

HTH,

Jon

cyril7

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Reply # 755392 4-Feb-2013 09:57

Hi, I have posted this info on a previous thread relating to fuel octane.

Higher octane rating does not mean more power or efficiency, it simply means that it has a higher knock rating, ie it will require a higher compression before it self detonates, thats all period, nothing else to know. Infact sometimes the material to create a higher knock rating may lower the actual potency of the fuel.

Engines have different compression ratios, generally a higher compression ratio can extract more energy from the fuel. In general engines of a specific size with higher compression ratios will deliver more power than an equivalent engine with a lower compression ratio. Its fair to say that most european engines run higher compression ratios compared to similar sized asian cars, but obviously each brand has its GTI model that will normally have a higher compression ratio and therefore may require 95 octane as opposed to 91 octane.

It should also be noted that even with a higher compression ratio very few if any engines will access all the energy in the fuel, they just are not that good regardless of fuel used or compression ratio, by this I mean even an engine setup to run a high compression ratio that requires 98 octane fuel will not even approach accessing all the energy thats available in even 89 octance fuel, its all about pre ignition or knock. So by this I mean the energy in the fuel regardless of octane rating is pretty much the same and even then any engine can only access a portion of this.

As a result if you car is designed to run on 91octane then just use that, putting a higher octane rating in will result in no improvement in any aspect.

As for 95/98 octane, most euro engines and higher performance engines across all brands require 95 octane or higher to stop knocking, put 91 one in them and they will run like dogs and potentially blow the top out of their pistons.

Hope that helps.

Cyril

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qwerty7

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Reply # 755407 4-Feb-2013 10:09

Dairyxox: Another thing to consider is the availability of 95 octane fuel.

I have a car which is supposed to run on 95 but it is impossible to purchase in my area (I live in Tauranga). Most service stations here sell 91 & 98. So you pay a premium to keep your 95 car healthy.

?????????? Caltex, z and mobil all have 95.

shrub

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Reply # 755520 4-Feb-2013 13:20

I use 95 in every car I've owned i never put watered down crap in the tank- I currently have a 20 year old Mazda 250k on the clock 1600cc. It runs like a 20 year car on 91. 95 just has that power and less hesitation under load. The old Toyota Caldina I had before was hard to start on cold days with 91 but 95 was mint.
On a side note Europe only has 95 and 98 none of there vehicles should run on 91 but people do cos its cheaper and they dont care what damage they could do to there engines.

scuwp

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Reply # 755545 4-Feb-2013 13:55

This is always a hotly debated topic and one that has been on GZ before.

I am firmly in the premium (95) gas camp, no matter what the car. Yes it costs more, but the vehicle/s run better, it is cleaner burning, and by my own 'real life' testing I get a little bit more distance per litre, so the added cost is negated by slightly better mileage.

I have not found any difference between 95 and the 98 touted by BP, with the 98 having a ridiculously premium price I tend to avoid it where possible.

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Reply # 755558 4-Feb-2013 14:22

jonherries: 95 RON tuned car with 95 ~ maximum efficiency
95 RON tuned car with 91 ~ less efficiency, increased engine wear and less power, not worth it

91 RON tuned car with 95 ~ a little bit more efficiency/power maybe, not worth it
91 RON tuned car with 91 ~ maximum efficiency

Correct, apart from the 3rd one.
91 RON tuned car with 95 ~ No benefit, just less money in your bank account.

shrub: I use 95 in every car I've owned i never put watered down crap in the tank.

*sigh*. Octane rating isn't a measure of how 'watered down' a fuel is, it's a measure of it's knock resistance. 95 fuel is actually in fact more 'watered down' than 91 (if only very very marginally),by the addition of anti-knock components to the fuel.

If you use a higher octane fuel than your car is designed for, you are simply wasting you money. There is no more 'energy' contained in a higher octane fuel and therefore there can be no benefit.

OTOH, If you use a fuel of lower octane than your car was designed for, the car will knock (fuel will ignite too soon), and your ECU will adjust the timing to stop the knock, at a cost of efficiency. Doing this long term can lead to carbon build up in the cylinders etc.

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cyril7

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Reply # 755562 4-Feb-2013 14:29

ajobbins:
*sigh*. Octane rating isn't a measure of how 'watered down' a fuel is, it's a measure of it's knock resistance. 95 fuel is actually in fact more 'watered down' than 91 (if only very very marginally),by the addition of anti-knock components to the fuel.

If you use a higher octane fuel than your car is designed for, you are simply wasting you money. There is no more 'energy' contained in a higher octane fuel and therefore there can be no benefit.

Correct, Toluene and Xylene are used to water down raw stock fuel to improve its knock rating, but DO NOT increase the energy of the fuel infact reduce it.

An engine that NEEDs higher octane fuel due to higher compression ration will extract more energy from the fuel regardless of its octane rating assuming you could stop the knocking and maintain correct timing, but an engine that will not knock on 90 fuel will not benifit from higher octane fuel.

Cyril

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Reply # 755578 4-Feb-2013 14:50

91 is being sold in nz not as pure as it should just need to to see whats happening with gull and there butane mix without conumers being informed

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Reply # 755582 4-Feb-2013 14:59

What I don't understand is ... Made in Japan ron100 why would they tune to 91. Made in euro pe Ron 98. Why would they tune to 91

You mean nz new cars are all detuned apart from falcon, Holden and the Camry?

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Reply # 755609 4-Feb-2013 15:14

This 95RON started because I have been looking at a Suzuki Alto that is on special for $15K and comparing that with Toyota and Nissan small cars.

Cheers

Gordy

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Reply # 755612 4-Feb-2013 15:18

Well the Alto has a 11:1 compression ratio, so yes it would need 95, kind of stuffs the running costs of such a small car up.

Cyril

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Reply # 755615 4-Feb-2013 15:25

I have an as new, low Km, 2012, top-of-the-range Toyota Yaris YRS for sale..that runs nicely on 91 octane :-)

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Reply # 755891 5-Feb-2013 08:30

scuwp: I have an as new, low Km, 2012, top-of-the-range Toyota Yaris YRS for sale..that runs nicely on 91 octane :-)

What colour and how much?

jonherries

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Reply # 755928 5-Feb-2013 09:53

ajobbins:
jonherries: 95 RON tuned car with 95 ~ maximum efficiency
95 RON tuned car with 91 ~ less efficiency, increased engine wear and less power, not worth it

91 RON tuned car with 95 ~ a little bit more efficiency/power maybe, not worth it
91 RON tuned car with 91 ~ maximum efficiency

Correct, apart from the 3rd one.
91 RON tuned car with 95 ~ No benefit, just less money in your bank account.

shrub: I use 95 in every car I've owned i never put watered down crap in the tank.

*sigh*. Octane rating isn't a measure of how 'watered down' a fuel is, it's a measure of it's knock resistance. 95 fuel is actually in fact more 'watered down' than 91 (if only very very marginally),by the addition of anti-knock components to the fuel.

If you use a higher octane fuel than your car is designed for, you are simply wasting you money. There is no more 'energy' contained in a higher octane fuel and therefore there can be no benefit.

OTOH, If you use a fuel of lower octane than your car was designed for, the car will knock (fuel will ignite too soon), and your ECU will adjust the timing to stop the knock, at a cost of efficiency. Doing this long term can lead to carbon build up in the cylinders etc.

I am glad I hedged that third one with a "maybe" and a "not worth it"

Jon

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Reply # 755962 5-Feb-2013 10:45

Relevant.

N

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