What petrol to use?

[JimO]

i have been using 91 in the raptor but at the first service the mechanic suggested i try 96 which i have , what do use fullas use - for those that dont know the bike has a TL 1000 V twin suzuki motor

[TS99]

always go with the manufacturer recommendations.

[Oakie]

The mechanic where I go told me they use 95 on all their bikes, even if the recommendation is 91. This is because '91' on a petrol pump is more of a trade name rather than an accurate indication of the octane. The octane out of a '91' pump may be less than 91. It's a bit like a bike being labelled a '250' when in reality it is only 225cc

[James Deuce]

The same comments that have been passed for 91 apply to the other octane "ratings". NZ uses the RON (slap happy she'll be right) system of measurement rather than the more robust DIN (German precision) system. Japan uses DIN. Our Octane ratings are already 2 points (approx) behind the reccommended levels.

Contrary to popular opinion higher ratings are ONLY required for engines with relatively high compression ratios (12:1 or more). Higher octane fuel has a slower moving, cooler flame front and a compression ratio under 11.5:1 will result in unburnt fuel and carbon deposits from 98 fuel. 89(DIN) is perfectly acceptable for most modern engines, thanks to modern ECUs and sensors 87 will be fine too. Where did I get this stuff? Kevin Cameron. He knows more about physics, engine design and management and just plain motorcycles than all of KB's database combined and he can regurgitate in a way that an idiot like me can understand.

You're basically chucking money away on dearer fuel. It's called marketing. We all know what kind of people get marketing degrees.

[TygerTung]

It depends on timing as well.

Even in my 1975 corolla with the 1500 5K innit it pinks on 91 and that only has about 9:1 compression or there abouts, so I have to run it on 95+ because the timing is a little more advanced than the manufacturers specification.

I don't run 91 on anything, even my scooter , don't like the stuff, but thats just me.

My 2 stroke has very low compression but that even still melted a piston on 95, although it was getting a bit hot.

Theres more factors to detonation than just compression.

[James Deuce]

There sure is, and you can cold seize a two-stroke on avgas.

I get the best mileage and the bike seems to run "sweeter" on Caltex 91 than anything else. The CB400 I had was the same.

I had a FIAT with a 9.5:1 compression ratio that demanded 98 octane - more to do with timing than anything else. It would pink like mad on anything lesser.

But we're talking about modern bikes and they're a lot more flexible in fuel requirements.

[Steam]

Despite reading all the zillions of threads on this over the past few months, I'm still confused.

[TS99]

We all know what kind of people get marketing degrees.

What kind of people are they Jim?? *** says guys with Doctorate in life **

[Titanium]

The K1200S runs a compression ratio of 13:1.

Here in OZ I put Shell V-Power Racing (avaliable at the pump) 100 Octane with 5% ethanol.

The handbook states to run a minimum octane of 95, preferably 98 octane or higher.

The 100 Octane is the shizz nizzle and at ONLY $1.30 Oz per ltr.

The 6.0 Ltr SS-V Commodore runs like shit on the stuff.

cheers


peter

[90s]

You're basically chucking money away on dearer fuel. It's called marketing. We all know what kind of people get marketing degrees.

I have to say that I run a Eunos 500 (v6) which barely moves and drinks like a fish on 91. On 95 it flies and still drink like a fish, but at least gets 100k more per tank than on 91. On the rare times I see 98 things are even better - worth the extra in better economy.

Both bikes I have had in NZ (2s single & 4s 4) also perform better in terms of power and fuel economy on 95 than on 91. The difference was marked (although our marketing majors might say this was not a double-blind test). I tried only 1 tankfull to be convinced to stick to 95.

Why don't you simply try the different fuels in your bike and see if it pinks, keep a note of economy etc? The price difference between 91 & 95 for a 20l tank bike is currently only a dollar.

[peasea]

The same comments that have been passed for 91 apply to the other octane "ratings". NZ uses the RON (slap happy she'll be right) system of measurement rather than the more robust DIN (German precision) system. Japan uses DIN. Our Octane ratings are already 2 points (approx) behind the reccommended levels.

Contrary to popular opinion higher ratings are ONLY required for engines with relatively high compression ratios (12:1 or more). Higher octane fuel has a slower moving, cooler flame front and a compression ratio under 11.5:1 will result in unburnt fuel and carbon deposits from 98 fuel. 89(DIN) is perfectly acceptable for most modern engines, thanks to modern ECUs and sensors 87 will be fine too. Where did I get this stuff? Kevin Cameron. He knows more about physics, engine design and management and just plain motorcycles than all of KB's database combined and he can regurgitate in a way that an idiot like me can understand.

You're basically chucking money away on dearer fuel. It's called marketing. We all know what kind of people get marketing degrees.

A lot of what you say is true and you obviously have some reliable sources. I built racing engines for nigh on thirty years and detonation/pre-ignition and flame fronts were things I studied in some depth. A high compression ratio (I'm sorry to disagree with you) is NOT the only factor to consider when looking at octane ratings etc. For example; comparing two different styles of combustion chamber will possibly clear the air.

A large cylinder with a relatively inefficient port/chamber configuration, two valves per cylinder, a compression ratio of (say) 10:1 and a given ignition curve will require a higher octane fuel than an efficient port/chamber configuration (read pent roof, for example) with multi-valve layout and the same compression ratio and ignition curve. Forget the compression ratio, forget the timing, call them the same. The more efficient port/multi-valve, pent roof chambered engine will run ok on lower octane fuel, the other won't, I can assure you.

Theorizing is one thing, doing is another and the dyno is a very useful tool. I've built Chevy's with conservative compression ratios that required careful distributor tuning to run on 'super' pump gas but the same size engines with more efficient cylinder heads (port,valve/chamber configurations) could go much higher in the compression ratios, use more intial ignition timing and run way more total ignition timing while making more power and not detonating.

There are so many variables, like squish and swirl to consider, then technical terms such as adiabatic expansion and chemical dis-association creep in but until shit like that is explained it's difficult to grasp the importance of octane. The fuel we have in NZ is basically cheap crap by comparison to overseas. Gull is made outside NZ, it is made to meet higher specifications so their base fuel at 91 will exceed our 91, I promise you. Their Super is great and so is BP's Ultimate 98.

Simply put; if your engine is tuned correctly (ie, the ignition timing is right and your plugs are correct) then try 91. If it 'pinks' go up a grade. That noise you hear is damaging to your engine, particularly rings, pistons, bearings and head gaskets. If you modify your engine and different camshafts enter the frame, or a higher compression ratio, then use the best fuel you can find. What's a few cents to preserve your efforts and your engine?

If in doubt; use the best.

[Hitcher]

Cheap is good!

The sticker on the tank of my (former) ST1300 said to use 98. I used 91 with no ill effects performance-wise. The inexpected termination of the ST was in no way related to the fuel in the tank.

[James Deuce]

Why don't you simply try the different fuels in your bike and see if it pinks, keep a note of economy etc? The price difference between 91 & 95 for a 20l tank bike is currently only a dollar.

I've actually done that very test and published the results on here. I got a massive variation in mileage and performance between manufacturer and octane rating. The difference between Shell 91 and Caltex 91 was 50 kms per tank on average. None of the higher octane fuels matched the mileage of the 91 fuels.

For my bike, running it on anything other than 91 is costing me money, and even saying that running it on Shell 91 is a hiding in terms of cost.

peasea, you're not disagreeing you're fleshing it out.

Simple rule of thumb for bikes:

Race Rep: 95, or higher if you feel like chucking money away

Italian Race rep: 98 Octane

Modern BMW: 98

Everything else: Go by the Manufacturers recommendation. 91 should be fine if your engine is healthy. But stick to Caltex is you can manage it.

Caveat: if it pinks go a grade higher as peasea says.

[vifferman]

The VifFerraRi runs better on 98 (go figger - it should give less power, as it doesn't have a knock sensor) mainly to stop pinking when the engine's hot, but in the winter I swap to either 91 or a mix of 91 and 98 (alternate fills) as it doesn't start as well on 98 when the weather gets cold.
I avoid 95 as I've had very bad results in the past with my previous VFR. The plugs are teeny-tiny ones, and get fouled with all the extra xylene/toluene the Big Four bung in to raise the octane rating.

[Bass]

I too have played with racing engines a bit and so done some study on the causes of pre-ignition.
I tend to agree that most modern bikes should be pretty happy on 91 (with some exceptions as previously mentioned). So I was surprised to discover that the Sprint HATES 91. I have been forced to use it once or twice (e.g. refuelling at Te Araroa) and she really rattles when asked for anything more than a tootle when on 91