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High octane fuel and the truth

SweetWagon

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Remember, a higher compression ratio is the only reason that you would ever need to change from regular fuel to premium...no other reason.

It not only high compression engines that require it. Force inducted engines (which usually have a lower compression ratio than naturally aspirated engines) also requires higher octane fuel to resist pre-ignition of the hot/compressed intake charge. Also I believe there is *some* performance benefits to be had as premium/higher octane fuels burn much cleaner/more efficiently = more torque, and the engine can be tuned to run more timing advance which also produces more torque and better fuel economy. My 2c
 

Super_Low 91

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may not be valid but iv got a maced tuned vn i put a full tank of 98 in it a week ago, the car has done almost 500km with a GPS to confirm it, an the fuel gauge is just on the red now,, thats a vn that doesn have your fancy lean cruise mode or anything, an thats a combination of both highway an round town
 

kane88

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one_and_only2004

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may not be valid but iv got a maced tuned vn i put a full tank of 98 in it a week ago, the car has done almost 500km with a GPS to confirm it, an the fuel gauge is just on the red now,, thats a vn that doesn have your fancy lean cruise mode or anything, an thats a combination of both highway an round town

How big is your tank?
 

azkwazere

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may not be valid but iv got a maced tuned vn i put a full tank of 98 in it a week ago, the car has done almost 500km with a GPS to confirm it, an the fuel gauge is just on the red now,, thats a vn that doesn have your fancy lean cruise mode or anything, an thats a combination of both highway an round town

Your point? My VP (same engine) got 550kms regularly on 91RON... thats average for a VN/VP. Both city/country..

aZk.
 

burnz

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with higher octain fuel the higher compression ratio you can run and or the more timing advance you can pull. (tune)

the higher comp ratio the less timing avalable, so an increase in ron allows more scope.

remember the higher the "ron" the slower the fuel burns, requiring more timing advance. without it your wasting money.
 

MasterOfReality

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With so many guys on here talking about using 95 RON, 98 RON and higher, and claiming to make up to 30% difference in power output, and so many others asking whether this more expensive fuel is going to benifit them I just thought I'd start a thread to help educate people and dispel some common misconceptions.

1. If your engine is not designed to use premium fuel, it will not benefit.
When I say 'not' I mean in any noticeable way. Sure, you may get a 0.2 or 0.3% change in fuel use or power output, but it is barely measurable, and certainly not noticeable.

2. Premium fuel is not 'better quality' or cleaner than normal unleaded.
Believe it or not, all fuel comes from the same place. It is all refined and then put into storage containers. Chemists then add chemicals to this fuel to determine what it will be called ie. Premium, ultra, regular etc. In fact, premium fuel has more chemicals added to it than regular unleaded.

The deciding factor for which manufacturers designate the engine to use, is DESIGN. The design of the engine (generally the compression ratio of the combustion chamber) decides whether the engine will NEED high octane fuel, or not. Engines wil compression ratios of 8 or 9:1 do not need premium fuel, nor will they benefit. It's not a choice that manufacturers they make, it's a need.

Standard Commodore engines do not need premium fuel, nor will they benefit from it.

I just hear so many stories of people wasting their hard-earned money on premium fuel and not realising that it's no better than regular. Their mate told them that they got an extra 50 km or 100km from a tank, or they think their car 'feels' better with it. One-off anecdotes unfortunately do not make good proof.

There's one main reason fuel companies push it onto consumers (apart from those few that actually need it), because it is more profitable. More $ for the same product. They don't lie, a 0.08% fuel consumption decrease is a decrease, but they happily leave this data out of the marketing dribble.

If you want to know more about it, then I recommend you read some engineering books, or peer reviewed documents (not a forum or manufacturer's website). Please don't waste your money.

I am happy to answer any questions/comments/disagreements that you may have.

Yes, I believe it.

hmmm... nothing that I'm allowed to publish online. All too complex and long winded anyway.

I have heaps of books, articles and journals that I studied from, but, being on a forum, this post was more to educate people than to prove or justify my words.

I will, however, answer as best as possible.

Nothing illegal about posting references, whether they are journals, books or conference papers. If you post something in the public domain you need to back it up.

Yeah. I am no expert but I think the later commodores can run better on higher octane fuel as they can adjust on the fly with the knock sensors.

Yes.

lol nah holdens too cheap for that..
Not sure bout VE's but I know VY VZ were tuned to run 91.

Though the more exotic holdens like monaros and clubbys ect.. were tuned to run the higher octane.

My 1991 HSV Enhanced VP Calais V8 comes equipped with a knock sensor from factory, as did many other early HSV's. There is a slightly noticable difference between fuels in my car, and that includes performance and fuel economy.

It was obvious you where going to get upset people posting crap right from the start. As soon as you tell people they have been wasting money on something that is only better in their head their going to winge. I only run 95 RON when I put injector cleaner through my tank other than that, S pack tune VN runs smooth as on 91 RON.

Bingo!

In my suzuki daily it makes sfa difference whether I use standard, E10 or premium, as it was designed to run on 91.
 

stroked

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with higher octain fuel the higher compression ratio you can run and or the more timing advance you can pull. (tune)

the higher comp ratio the less timing avalable, so an increase in ron allows more scope.

remember the higher the "ron" the slower the fuel burns, requiring more timing advance. without it your wasting money.

Agree with you 100%
 

Calaber

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I don't bother with premium unleaded in my VY 2 V6. In fact, I regularly use that evil E10 because a) that's all that's available around my place and b) I don't accept the crap that's been written in this forum about the dangers of using it.

Recently, I drove to the Sunshine Coast from Wyong up the New England Highway for a bit of a change of scenery. I travelled from home at Wyong to Stanthorpe in Qld before having to refuel and the car has the standard fuel tank. It cruised smoothly all day between 80 and 110 (depending on the prevailing speed limit) and when I needed to overtake, it performed as it should. I had travelled over 800km and still had 120km to empty on the trip computer.

My point? (A) - you don't need to run premium unleaded to get outstanding economy, and (B) using E10 doesn't perceptibly affect economy either.
 
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