What octane do you put in your tank?

  • Thread starter Thread starter riivaaja
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I've heard that running too much octane in an engine can foul the plugs...is this true?
 
More octane means a more stable fuel - one less prone to exploding, basically. If you run fuel with too high an octane for your engine to burn, you'll be left with a lot of unburned fuel and susceptible to any issues associated with running rich.

You should always run the lowest octane (least stable) fuel your engine can use without knock.
 
93 octane from Shell, Mobil, or BP. This winter I've been using Speedways 92 octane though.
 
Famine
I've amended the poll with the rough approximations of RON values to US "octane" ones. It's not quite exact - in fact there's no reason at all why 95 RON petrol couldn't be the same as 81 octane gasoline - but generally PON is 8 higher than MON, and RON (which is [PON+MON]/2) comes out about 4 higher.
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Thanks Famine 👍

In that case then, I'm on the equivalent of 91. I've not tried anything better in the Mazda yet. I did a few times in the Fiesta and apart from possible cleaning benefits it didn't make a blind bit of difference to anything else. I wasn't keeping tabs of my fuel consumption back then so I'm unaware whether it gave me any benefits in that department.
 
I use 95 Octane Australian, what ever that equates to in the rest of the world. Without an ECU using a tune for 98 there's no point in going higher.
 
Jondot
I've been tempted to try mine on the likes of V-Power and Ultimate, but any research I've read has proved inconclusive when it comes to performance benefits (or the benefits are so small that they might be down to the decreased weight in the driver's wallet).
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US octane numbers are the average of MON and RON (R+M/2).

It depends completely on what your car is optimized for. Lower grades of fuel actually contain more power per volume than higher grades do, but because of this, they are more likely to detonate (knock or ping) due to spark advance or high compression. Higher grades are less explosive and actually make less power per unit of volume.

The TSX and the 3er are designed to run on 91-93 octane, so I put 93 in them. To make the most power, the ECU advances the timing until it senses detonation. If you put lower grades in, it just retards the timing until the knock sensor tells it OK. It won't hurt the car but it will degrade performance. But putting 100 octane race gas in the car would also degrade performance, and cost twice as much. Nothing that is not high-boost or high-compression can take advantage of that high an octane rating.

All cars have a point past which the ECU will not advance the timing. I don't put anything higher than 89 US in the Subaru or the van, because the amount of spark advance that would be supported by 91-93 is outside the parameter table of the ECU.

For brands I like Sunoco, Mobil, and Exxon, but I mainly go by price, and brand as a secondary consideration. Any of the lower grades, in fact, are commodity gasoline and are supplied by the closest refinery regardless of brand. Around here, everybody's low-grade fuel is Sunoco, even at Exxon stations, because there is a local Sunoco refinery.
 
I suspect Jondot's SportKa won't be "optimised" for anything more than regular fuel, given that it's just a Duratec 1.3 re-bored to 1.6 litres. In this form it's only marginally more advanced than the old Endura engine in the previous Ka, which itself was development of the Kent engine first seen in the late 50s/early 60s...
 
Joey D
You guys seem to have crap fuel in Canada or at least at the Esso I went to when I was there. I got 91 octane and I then managed to drop 5 mpg from my average for US fill ups. Maybe the car just wasn't tuned to run on it, I don't know.
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Esso in Ontario is pretty much known for their crappy fuel. Most stations are nothing but "no name" fuel with an Esso owned smoke/snack shack. Shell, some Petro-Canada's and Sunoco are basically the places to go, atleast around here.
 
Seeing as how I've got a Camry-powered Celica, I usually fill up with 87 at the local Shell or Speedway. When I'm feeling frisky, I'll run 89. But usually not. That big lump of an engine doesn't need or deserve it.
 
I stick regular 95 RONin my 2 as I've not noticed any difference in performance with V Power. I do occasionally stick a tank of the V Power in the Mazda though (usually when the wife has gone in to pay).

I used to use that all the time in the Leon 20VT I had as it seemed to make the turbo spool up a little quicker and I certainly got a little more mileage out of each tank meaning it effectively cost no more.
 
The GTI is turbocharged, direct injected and runs a higher compression so of course it gets 93 octane Shell V-Power.
 
87 for both the 740 and the Barracuda, although I know they deserve better.

I ran the Barracuda on 89 once and she really liked it. If I had the engine the way I wanted it she'd be running 93. Apparently there's a place around where I live that sells non-ethanol gas, definitely want to try that with the barracuda sometime.

The 740 will run on 87 but it likes the higher octane much better. I've never put 93 in it, mostly because the cost, but I've heard that it will run 93 perfectly fine.
 
My manual says I should use 93 octane, so I do.

When I first got it, it got nothing but BP 93 octane for the first 6 months. Then for the first 6 months after I moved, I switched to Shell 93 because there's only one BP in town and it's out of the way. After those first 6 months in the new town, I started using ethanol free 93 octane from a small mom'n'pop gas station, but their card readers on the pumps broke so I quit going there. I now use Chevron 93 mostly because their card readers on the pumps work, and its literally at the end of my street.
 
horde_r35
Exactly:tup:! My tuned K20 has 0 knocks with 109 octane! I think its 109 (US measure) coz the SUNOCO is imported from the US... Does anyone know for sure?
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I very much doubt it is 109 octane, which would be very high grade aviation fuel. Race fuel for built gasser engines is typically 100 octane (R+M/2). If it is 109 octane it would be hideously expensive, to the tune of 3x-4x the price of consumer gasoline.
 
Duke
I very much doubt it is 109 octane, which would be very high grade aviation fuel. Race fuel for built gasser engines is typically 100 octane (R+M/2). If it is 109 octane it would be hideously expensive, to the tune of 3x-4x the price of consumer gasoline.
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It is - and it's 3-4 times the price of European consumer gasoline - which makes it something like 10 times the price of American consumer gasoline.

It's also important to note that it's point-of-use fuel - it loses octane by being exposed to the air or sunlight and should only be bought in quantities you're going to use immediately. It will decay in the fuel tank. In an engine that is suited to use it (the drag Dodge with the 572 is a candidate; a low compression, naturally aspirated K20 is not), you will be seeing benefits of the order of 25-40% more power or more rather than sub-10% values horde_r35 is claiming - which only arise because of the ethanol content shovelling more oxygen into the cylinders.

The net effect is that this Civic (which, if we remember, can break all the known laws of automotive physics as it slips through the air with the efficiency of a drop of water) will be literally pissing unburnt fuel out almost as fast as he pisses his money up the wall. 109RON in a low compression, low capacity, low power engine is nothing more than an extremely expensive willy-waving exercise.
 
YSSMAN
Seeing as how I've got a Camry-powered Celica, I usually fill up with 87 at the local Shell or Speedway. When I'm feeling frisky, I'll run 89. But usually not. That big lump of an engine doesn't need or deserve it.
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At least it's not a Corolla-powered Celica. 👍 I've put 89 and even a bit of 91 in mine a couple times, never again.
 
You know I just took a second look at the poll....Does any Manufacturer require 89 octane? Seems like nobody uses it....
 
I used to have a chev 350 I would fill with reg then add 4 or 5 ounces [maybe tablespoons]of tolulene and really improve performance but since I don,t remmber the proper mix I would not advise you experament exspcialy on newer cars but I know I was saving 18 cents a gallon and at the time that matterd
 
Thatman
You know I just took a second look at the poll....Does any Manufacturer require 89 octane? Seems like nobody uses it....
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I use 89 octane in my Mazda, because the ignition timing has been advanced. It could still run on 87, but it will knock in certain situations. As far as I know, no car has been designed to run on 89. It really wouldn't make sense to do that. Of course, no new car really requires premium, either...the ECU will detect lower octane and retard the timing accordingly to protect the engine.
 
My car ran weaker on lower octane grades when it was stock, but no real issues. Some other guys got hesitation, though. It's built for 95 RON (giving a measly 10 horse hike over the regular Protege/Laser), but the knock and oxygen sensors allow it to adapt to lower grade fuel if that's all you use.

Did the distributor advance trick before on my previous car. Didn't see enough benefit in power to justify the extra cost of gasoline, so I tuned it back.

It's buggy that many Japanese market cars come over here requiring 95 RON. On engines with barely enough power to stay lit when you turn on the AC. :indiff:

RE: Toulene: Friend did the testing before with acetone... EFI engine. Minimal gains (almost miniscule, in fact) in economy for the amount of effort put into it.

horde_r35
I just dont understand and nerver did, why people are so suspicious around here! Why do people begin with suspects in the 1st place is a strange thing to me! After i post the Dino run, i bet someone will say its from a friend or something like that! If i said i had a porche 911 turbo and showed you a pic of me inside the car will it be valid?! Do you understand where im getting at? No one can really proof anything at a forum:indiff:!
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If you've got the money to modify a car and dyno, you've got the money for a digital camera. Or even a cellphone camera.

I don't know anyone who modifies their car nowadays who doesn't take a few snaps here or there of his car, his car on the dyno, and the parts he's got on... and many dyno readouts will put your name or the car's registration plates on there... depending on the program.




- Half the horsepower! Twice the pictures!
 
Hi Guys,,

I am from ZA, our costal towns use 97 oct fuel.
our inland citys use 93 oct fuel due to they are 1000m plus above sea level,
This is due to the fact that if you use higher octane at inland citys 'high altitude', there is less oxygen the combustion chamber temperatures will run higher with a high octane rating.
if you have a street rod/racer and the engine has been tuned its better to run higher octane,, we run a common fuel here which is 102.6 racing fuel,, you can only use this fuel if you have the wright compression ratio,, plus wright head gasket is used. If not you'll have the cars engine start to detonat (ping). detonation is the biggest engine killer, even more if the ingnition timing is out, we normally set our cars timing up at 8 to 10° before TDC, max advance of 28° at 3000rpm

@horde r35
I find it hard to believe you get jet fuel.. 109 octane fuel our higher is classified as jet fuel... our none as avgass=aviation fuel
jet fuel is disigned around rotarty turbine engines full stop.
i can't see you getting 1kw plus from this type of fuel..
if you looking for power from fuel why don't you just us Nitro methane,, it a winner, but highly flammable plus its more commonly used in top fuel dragsters..
have fun guys. Ant.
 
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Superplus only in the Porsche.

Cheapest diesel available in the Mondeo.
 
horde_r35
To answer your question :http://www.aaoil.co.uk/racing-Sunoco-GT-PLUS
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Ahh, so it IS the GT260 PLUS. So, some confusion came up when I was looking at Sunoco's site.....first off is their list of unleaded fuels which I was referring off earlier, and just look at the Octane Rating here guys, the specs for the GT260+ is in the blue column, octane is 2nd item down:

Unleaded_RFcopy.jpg


So in that page it says 104 Octane.....and then next off we go to the direct page and then this comes up:

Sunoco_260GT_Pluscopy.jpg


Now it says 109 Octane........hmmm, Sunoco fail?
 

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