Fuel Thread - octanes, consumptions, what does it all mean?

donki

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The be-all and end-all of fuel threads!

Octane:
This is a rating given to how resistant a fuel is to burn. This means the higher the octane number, the more compression the fuel can withstand before suddenly igniting (preignition or detonation). The main measurement of Octane is Research Octane Number (RON). A whole bunch of factors come into play when choosing a good octane fuel (such as when intake temps get too warm, timing is retarded in order to prevent detonation, as well as receiving feedback from the O2 sensor, but thats for another thread).
A higher octane fuel is required in a high compression engine as a high-comp engine often has issues with detonation/pinging e.g, turbo engines, being higher compression need higher octane fuels. Non-turbo and low compression engines can run happily on lower octane fuels. The 4G15 and 4G93 is considered to be on the low-mid range of compression (V8's tend to be lower compression, while some cars like Honda's are much much higher compression)
Note: Our cars do not have a reference for knock, and therefore cannot advance timing automatically to suit the more resistive knock capabilities of higher octane fuel (see below). Running higher octane and thinking it "runs better" is a placebo effect on the CE. It will not get more km per tank, it is your right foot that is doing that. Higher octane fuels tend to have more detergents, thus cleaning your fuel system, but the car having an old tech style narrowband Oxygen sensor doesn't see any change in the O2 levels, so it still sprays the same amount of fuel for 91 or 98, so you get the same km/tank as always.

The lower the octane the fuel, generally the faster it will tend to burn. As you may know, advancing timing can allow for more power (crash course in timing: you want all fuel burned by around 15-18 degrees after Top Dead Centre, so you advancing timing (to before TDC) to hit that point. The faster the engine revs, the more timing advance. Too much advance, and you get pinging and slowly ruin your pistons and bottom end bearing. Too much heat in the cylinder, pre-ignition and detonation. Too much timing retard, and you get no power or eventually burn out exhaust valves) Tuning theory philosophy is you want to only use the minimal amount of advance as possible, called MBT, or Minimum Timing for Best Torque, and this is what a dyno tune will do (dyno run to get power numbers, advance timing, dyno run to see where it changed, repeat until knocking, then back off a couple degrees).

-In Australia, we sell regular unleaded 91RON, premium unleaded 95RON, and premium 98RON. Some Servo's sell 100RON as well, but these often have a blend of Ethanol in them (2017 edit: a lot of 98RON and higher fuels are at least 5% ethanol)
-Diesel engines run basically off compression ignition, and as such have very low octane ratings - between 15-25RON.
-Methanol/Ethanol fuel is around 107-108RON~
-Aviation Gas (AvGas) has high octane, up to 130RON~ (2018 edit: you need a pilots license to purchase it now, as it's recorded against your license).
-In the USA, they use AKI, which is RON+MON/2. MON measurements are a little more tighter than RON, being preheated and engine ignition advance and using the knock sensor to get a reading.


Consumptions:
-All Mitsubishi CE's have a 50L fuel tank. Your fuel light will start slowly flickering on with around 15-12L left in the tank. It will stay on when you have around 10L left. Due to the design and shape of the fuel tank, the top quarter, and the last quarter of the fuel tank take much longer to drain (ever noticed the 2nd and 3rd quarters go really quickly).
-98% of us on Auslancer will get between 350km/tank to 650km/tank. There are a couple exceptions however (those running boosted cars, or different fuels or engines). To try to increase kms per litre, change to a clean air filter, change O2 sensor, and reset the ECU (unplug the battery for 10mins and drive again gently for 16mins+)
Note: Due to having older engines (The 4g15 and 4g93 is a design from the late 1980s) thats are not as technologically advanced as your Mum's XR6 turbo Falcon, we dont need anything higher then 91RON fuel. Even when running (low) boost, a good tune with timing set 100% correctly, you can be relatively safe on 95RON, however you can rest easy with 98RON or above.
Note 2: New model Lancer's have a knock sensor, and will automatically advance timing to suit the new fuel until it knocks, hence "giving" more power - it actually has its "max power" state, and when a low quality fuel is added, it will retard timing until the problem goes, and then slowly return back to normal.

Note 2 on tuning: The 4G15 and 4G93 is tuned very rich at Wide Open Throttle from factory. You cant smell this, only specific equipment is able to detect this minute change, which is something between 13 grams to 15 grams of fuel vapour in 200grams of oxygen between rich and lean. When you advance timing to its limit (MBT or knock), a common cheat way to keep it safe is to make it very rich. Leaning it out or changing the peak cylinder pressure point will yield a decent power increase, this is done by a tune, or by choosing a fuel that burns faster or slow. Low and behold, Mitsubishi designed the engines with 91 octane's flame speed in mind, so putting any other fuel in will really only clean the system and not really give power.

E10:
E10 is usually 95 octane fuel, and is made up of up to 10% ethanol (UP to 10% is allowable in Australia by law, and up to 5% does not need to be listed). It is slightly more environmentally friendly, being made up of ethanol usually sourced from cane, and generally burns a little cleaner emissions-wise.
People tend to be scared of e10 for a couple of reasons; Carburettor cars don’t tend to run very well on e10, but it can all depend on the carby used. In addition, older cars (pre-1986) tend to have a lot of rubber fuel hosing, and this hosing doesn’t resist the solvent properties of ethanol very well. Our modern cars are fine to use e10, and using one e10 tank every half-dozen or so can help dissolve any gunk that is left in your tank – be aware that this can cause your fuel filter to slowly clog up from passing sediment, but that’s what it’s there for. I would not recommend leaving a full tank of e10 in the car for long periods of time, because although we use fuel hard lines almost the whole way through the car and the little rubber lines left are of a different makeup than their 1980s counterparts, e10 can cause some small corrosion to these lines over time, in addition to attracting smaller amount of water than e85.

E85:
E85 gets a special mention (not only cause it smells good). Generally speaking, E85 fuel is around 85% ethanol, and 15% fuel, however this is allowed to vary by a big amount (from 52/48 to 85/15). E85, being ethanol, is literally that - pure distilled alcohol with vomit-inducing chemicals added (so you can't drink it).
Also known as Corn or Cane Juice, is very resistant to detonation. This is partly due to the fact that, being ethanol, it has"cooling" properties that can cool an engine enough to stop the fuel going bang too early. As a result, it is used in a lot of boosted cars to up power & boost significantly more and still keep things running safely.
It is cheap too, being a byproduct of sugar cane or wheat, which Australia's top end has plenty of. The cons of E85 however, are that it isnt available everywhere that normal fuels are, that fueling consumption is a lot higher, and e85 can tend to attract water, but this water is "held" by the fuel. This is due to needs around 11% Air:fuel ratio by mass, compared to normal fuel at around 6-7% air:fuel by mass.

This means you need around 20-30% additional flow capability right off the bat for fuel pump and injectors. 30% more fuel means 30% more air needs to be pumped in, and for a turbo, thats simply dialing up the boost to suit.
E85, being very resistant to detonation (and pre-ignition), allows for additional timing advance that can be dialed in - on a turbocharged car, this results in a metric fk-tonne more power, but only a handful of horses for an N/A.

E85 does not "eat" the rubber in the CE fuel system. People confuse E85 (Ethanol) with Methanol. Meth, which is what the Funny/Drag cars often use, will etch through aluminium fuel systems and engines in no time. Ethanol is a solvent the same as petrol, and very very close to the same strength of petrol as well.
E85's ethanol component is hygroscopic, the same as E10, which means it absorbs water. Having E85 sit in a fuel tank for a long while will absorb water (the tank is not a fully sealed system., and cause it to separate from the petrol and cause a whole host of issues in the fuel system from rust to detonation. Best to use a tank within 1-2 months.

Expect to have a reflash or a full standalone ECU to take full advantage of any fuel change, even if its from 91, e10, to e85.


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Re: Fuel Thread - octanes, consumptions, what does it all me

I rear somewhere that e85 is bad for cars that weren't originally made to run that fuel because it will erode the engines seals, true?
 
Re: Fuel Thread - octanes, consumptions, what does it all me

grk2meet said:
I rear somewhere that e85 is bad for cars that weren't originally made to run that fuel because it will erode the engines seals, true?
i heard the same thing about E10 in older cars :p
 
Re: Fuel Thread - octanes, consumptions, what does it all me

I was going to ask about E10 actually, so many people have written it off but surely it can't be that bad if they are selling it so openly?
 
Re: Fuel Thread - octanes, consumptions, what does it all me

Mr. Andon, what will happen if i put e85 in my lancer :mrgreen:
 
Re: Fuel Thread - octanes, consumptions, what does it all me

E10/E85 will take a long time to erode any rubber connections in your car. Any car made after about 1989 i think it is contains a different type of rubber which is much more resistant to ethanol, and much of it was replaced by fuel hard lines anyway.
What happens more often, is the ethanol actually dissolves any junk and grit in the tank, and this in turn clogs up the fuel filter when it passes through the pump. This causes fuel starvation, and then engines go pop. I would not recommend you run a car on e85 without having it tuned on it beforehand, or upgrade the necessary parts (generally speaking, much larger injectors are needed, and a fuel pump to keep up supply).

Check out Shell's website. They have a pretty good list of cars that can use E10 without issues. Personally, i wouldnt run tank after tank on E10, but once every few fillups doesnt hurt.
 
Re: Fuel Thread - octanes, consumptions, what does it all me

Disappointed. I thought this was going to be a fuel consumption thread. I got all excited thinking I could post a pic of my fuel gauge.
 
Re: Fuel Thread - octanes, consumptions, what does it all me

As an idea, I run my CH almost exclusively on E10; once in a while when fuel's cheap I treat it to 95/98. Reasoning for that was I asked the previous owner and they did the same (say once every 5 tanks a 98 tank), and hey - car was still going fine when I got it 8 years old, so if it was gonna happen, it would have happened by then.

Now that you mention it, I should probably look into doing the fuel filter.
 
Re: Fuel Thread - octanes, consumptions, what does it all me

i'm pretty sure you're not meant to just switch between fuels as you like. whatever fuel you have when you change your oil you should keep using till your next oil change.
i filled up a few times with e10 when i first got the car, treated it to 98 once and it drove so much better and smooth so have stuck with that ever since.
 
Re: Fuel Thread - octanes, consumptions, what does it all me

I find that to be the opposite with my car. Fill it up with 91/95/98 and it runs as normal. Fill it up with e10 and it's got rockets on the back of it with a massive increase in low-down torque. I don't know why. I don't really care either. I always fill up with 91 unless I happen to rock up into a bay with e10, then I grab the e10. Tired of filling up with 98 and wasting my money, that can wait until tsututu.
 
Re: Fuel Thread - octanes, consumptions, what does it all me

E10 will run leaner than non ethanol fuels at WOT. This is possible the extra power you feel.

98 will hit about 10.8 up top, while E10 will sit about 4 AFR points leaner about 11.2/3 up top.

When in closed loop the ecu can trim E10, and they will both run with similar AFRs
 
Re: Fuel Thread - octanes, consumptions, what does it all me

i basically go with - it's a low powered engine that doesn't need premium, so to hell with that - there's all of bugger-all difference running 91 to 98, and it costs an extra ~16c/L, so $8/tank, and at my driving (est 8L/100 given mixed metro and highway), another $268 a year in fuel.

No thanks.
 
Re: Fuel Thread - octanes, consumptions, what does it all me

Put E85 in my AE86 Sprinter, and it ran like *poo*. I was interested to see what it would do considering it had higher comp, and ran rich as anything with the factory ecu, but it was undriveable.

$268, but you get more km's per tank, so fill up less, so the $268 isn't a saving.
 
Re: Fuel Thread - octanes, consumptions, what does it all me

I use RON91 and E10 depending on the price and if I have a shopper docket, getting up to 500km out of a take before the light stays on, just depends if I've done some hwy driving.

Haven't really noticed any power or fuel consumption difference between them with the 4G93.

I have put in RON95 once or twice, just a waste of money for my engine.

FYI most Nissan's built before 2004 can't run E10, I've checked. My parents have a 99 Pathfinder and were told not to use it.
 
Re: Fuel Thread - octanes, consumptions, what does it all me

E85?

my fuel consumption is pretty much spot on the same with E10 and 98, so it's an actual saving (as opposed to false economy)
 
Re: Fuel Thread - octanes, consumptions, what does it all me

Ive used E10 for all my cars (except EVL20T) and every now and then i'll throw a tank of 95/98 in

Theres been tonnes of talk that E85 will eat your valves etc, we have been running Caltech Eflex (E70) fuel in mates GSR now for the past 4 years and having no issues

When I get EVL finished it will be tuned with a flex sensor and tuned on United E85 and 98PULP, so Im not running Ethonol for a long period
 
Re: Fuel Thread - octanes, consumptions, what does it all me

the issue with e85 is it may eat away rubber lines and seals. good thing our cars run either teflon or vitton seals aye
 
Re: Fuel Thread - octanes, consumptions, what does it all me

Small section on E10 added in
 
Re: Fuel Thread - octanes, consumptions, what does it all me

I do have a question about the 4G93p found in the M21 Protons, do they need the premium go go juice or will they happily run on the standard juice.

ETA - can it be converted to run E85... cost?
 
Re: Fuel Thread - octanes, consumptions, what does it all me

Will run on anything
 
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