PDA

View Full Version : Which is best fuel?



stevensaaron
5th March 2007, 20:08
Hi i have a 'Suzuki GSX250 Across'. Which is the best fuel for Power, fuel economy, etc. either 91 or 95/96 or 98. Thanks

Indiana_Jones
5th March 2007, 20:18
91 works for me pretty well.

-Indy

YLWDUC
5th March 2007, 20:26
Always stuck 95/96/98 into the duc, although that said I wouldn't be able to tell you if its a lot worse on 91. The higher the octane the better I reckon

Babelfish
5th March 2007, 20:33
My understanding is the more octane the more bang...that said they throw so much shite in the fuel you never know what your going to get, then theres the quality of the batch of fuel at the different stations.

I like using BP's 98 for cleaning (for my carbs too). The grunt increase isnt something I think my riding style would notice (read: Nana) so thats it really. Oh, and I like the big grunty handle on the pump so I feel I need a NBC suit n shite...the perfect consumer me!

Colapop
5th March 2007, 20:34
It depends on the age of the bike too, I think. Refer back to the manufacturer's recommendation. I think higher octane fuel burns hotter and can damage your engine but give greater power...?

Grub
5th March 2007, 20:38
I take 98 where I can get it, 95 at other times.

Because of the greater power, it is presumed that you use less throttle. That was the theory that got me using 98. I keep meticulous fuel/trip log records and there is some evidence to support that but it's not overwhelming.

On 95 I get 19km/litre, where I use 98 I get 20+km/litre. I've yet to do a $/km comparison ... mainly because I don't want to know my theory is rubbish. I like the anti-knock properties of the higher octanes since my bike is 11:1 commpression ratio

MidnightMike
5th March 2007, 20:40
I use 95 for my gsx.

Babelfish
5th March 2007, 20:54
Check out this link for some info: http://www.dragtimes.com/race-gas-fuel.php

Summary is that both regular and high octane fuels most likely have same cleaning power. Also note they mention other properties that better reflect how the fuel benefits the system re: cooling, cleaning and bang for buck.

I still like the big butty handle on the BP ultimate though, but I can help thinking people would stop laughing at me if I stood normally while filling with it, rather than like I was putting the flag on everest

Babelfish
5th March 2007, 21:05
Here's another link: http://www.ftc.gov/bcp/conline/pubs/autos/octane.htm

Another thing I read was someone saying to use the minimum octane rating that doesnt give you engine knock...of course, owning a vitter I'm not sure that test is approprate for me, it can sound like its exploding at the best of times.

The more I read the more I'm changing to regular...I wish it came with a cool pump nozzle handle

Babelfish
5th March 2007, 21:08
Last one: http://www.ethanolrfa.org/objects/pdf/2003motorcycles.pdf

vagrant
12th March 2007, 21:33
It's a bit of a fib that higher octane ratings equals more power. The rider is that the engine needs to be tuned for it. A higher octane rating basically means that the fuel can withstand a higher compression ratio before it starts self igniting, diesel engine style.
So the "more power" actually comes from the more effective use of your fuel/air charge by squeezing it tighter before you add the spark and make it go bang.

There are other additives in the mix that do things like controlling the speed that the flame front moves out from the spark, and perversly, increase the flashpoint of the fuel to make it less flamable and safer to store and handle.

What it all comes down to is,
if your bike specs call for 95 octane or higher, then use it, but if not, your wasting beer vouchers.

Babelfish
13th March 2007, 08:37
bloody good explanation there fella

imdying
13th March 2007, 09:12
Best fuel in NZ is the cheapest one that doesn't pink. Try a tank of 91 and see if it makes the death rattle. If not (none of my bikes have), keep using it.

Freakshow
13th March 2007, 09:25
I found 91 ran better for me in the GSX 95 just didn't feel right?

cbr guy
19th March 2007, 19:34
Best fuel in NZ is the cheapest one that doesn't pink. Try a tank of 91 and see if it makes the death rattle. If not (none of my bikes have), keep using it.

i've just changed to 91 after reading on here that it makes the bike run better. and on the ride home i noticed a random rattling noise. so its maybe from changing fuel. how damaging is this?does anybody know? Ive just filled up again so might have to just syphon it out

sanchez
19th March 2007, 19:43
i've just changed to 91 after reading on here that it makes the bike run better. and on the ride home i noticed a random rattling noise. so its maybe from changing fuel. how damaging is this?does anybody know? Ive just filled up again so might have to just syphon it out

It is bad, very bad, does it happen mainly at low rpm if you crack the throttle open a bit?

Drain it out if it's easy to do, otherwise mabye just chuck a bottle of octane booster in and put some 98 in as soon as you get down to 1/2 a tank or so.

peasea
19th March 2007, 22:38
I've posted other comments about fuel on this website, under the Touring banner, HD stuff etc, but the theory is the same. If your bike rattles (pinks, knocks, farts or otherwise objects) to cheap gas, then switch asap to a higher octane. What's a few cents to give your ride the best? The knock can be damaging (rings, pistons and bearings) so don't go grabbing big handfuls of throttle under load; ease it on and use your revs, change later and run the gas out, then go for the next grade up when you refill. The best gas I've found is Gull super and BP Ultimate. If you find the knock has gone then there's your answer. If not, go up again until, if you find the machine knocks even with BP Ultimate, you have a problem. In my experience ignition timing is often overlooked. I'm happy to share my knowledge of four-stroke engines (accumulated since 1973) and what I have learnt about their needs as to octane ratings. A lot has to do with the expectations of the operator, the loads and the conditions. Nana will get by on her own with 91 when she idles to the shops in her 1300cc shopping basket cage, but Joe(sephine) Throttlebug will have a different requirement when on the back wheel of his/her tyre-fryer at 160k's while Tony the Tourer will have another story when loaded up with saddlebags and a partner. I'm happy to share knowledge and experience but I'm no petrochemical expert. Neither am I a trying to sell something; I've built a few engines though. Email; pcwordsmith@xtra.co.nz.

imdying
20th March 2007, 08:48
i've just changed to 91 after reading on here that it makes the bike run better. and on the ride home i noticed a random rattling noise. so its maybe from changing fuel. how damaging is this?does anybody know? Ive just filled up again so might have to just syphon it out
Well, the death rattle isn't good, but I doubt you'll cause any immediate damage. Just dilute it out with 98, every few days top it up, that'll raise your overall octane. I wouldn't go the trouble of syphoning it. It's worth trying to figure out if it is pinking, or if the noise is something else. Random rattling is a pretty good description of pinking though... when does it do it? Lightly loaded, heavily loaded?

cbr guy
20th March 2007, 17:07
dam that sux! i was enjoying the cheap fuel!lol. i just noticed it while cruising at 100kmh, but didnt really think much of it because it could have been a loose fairing or something, but its not.i actually weighed myself wearing my gear before the ride and i was 80kg which shouldnt be too bad of a load for my cbr250. might just syphon some of it directly into the car and fill the rest up with 95 (can't get 98 in little old inverargill) to bring the octane up a little. now i've just got the challenge of driving my bike gently for 25kms before hitting the closest petrol station, cant be good.
thanks for the help guys, you probaly just saved my engine!lol

surfer
20th March 2007, 19:39
91 works fine for me, seems to run better than 98 or 95. I reckon you should all change to riding an older bike :yes:

Max Preload
20th March 2007, 20:06
Best fuel in NZ is the cheapest one that doesn't pink. Try a tank of 91 and see if it makes the death rattle. If not (none of my bikes have), keep using it.

The problem with that being high rpm detonation is the real motor killer and you're unlikely to hear it happening until it's all over.

Octane is a measure of a fuels ability to resist detonation and in a bike engine with higher compression ratios this is important. Higher octane fuels are slower and cooler burning so without adjusting the ignition advance, using a higher octane fuel will not result noticibly in more power.

At the end of the day however, using higher octane fuel in a motor designed for lower octane fuel will not be harmful. The reverse scenario is harmful. I always use 98.

imdying
21st March 2007, 09:15
The ignition curve on a CBR250 would cause it to pink at load at a lower rather than high rpm, the advance is reasonably quick.