AFAIK - the increase in summer mpg is down to simple physics. Modern fuel injection systems rigidly supply the correct fuel air mix depending on the precise atmostpheric conditions, and warmer (less dense) air needs less fuel to achieve the right mixture.

I hope this isn't complete cobblers!
Older carb systems didn't have the flexibility so were rather more approximate.

Nicola, just a cautionary note about using higher octane fuel in the Burgman 400's. You can use it of course, it's your choice but there has been much talk about this on the Busa site in the states and elsewhere. Yes, I know they get different fuels but the main problem with higher octane and the Burgman, and many other bike engines, is that it burns more slowly and as such it can burn your exhaust valves if you ride hard. The expelled gases are still burning as they are ejected past the exhaust valves and this is what can cause some problems. That's inspite of the hardened seats and valves now fitted to all engines. It can also lead to more carbon in the engine. Bikes are not like most modern cars where you can switch octane fuels at will. Cars have learning ecu programs which allows the engine to adjust your ignition and injection map to compensate for the slower burn. Most everyday bikes don't do that and can suffer. Of course bikes run a closed loop induction/exhaust system and will adjust mixture, but it doesn't' normally go further than that on bikes unless you have a GTR1400 Kawasaki of something big. The occasional gallon or two won't hurt but it may be worth avoiding the high end stuff for longer term use. Just my two peneth! I used Shell 99 octane in mine once because it was the only fuel I could get in the arse end of nowhere, and my engine made some unusual noises almost like pinking but of course on high end stuff it's probably wasn't. So I didn't hammer it. After refilling with good ol 97 ron it ran and sounded normally. Disappointed!

+1

I think everybody on here might know this by now, but:

High octane fuel is not more power fuel than low octane fuel

"high octane" means that the fuel is less likely to detonate under compression
It is linked to high performance engines because those engines have high compression (high pressure in the pistons), not because the fuel is more powerful.

It is actually harder to light and as Data said, slower to burn too.


Going back to the OP, I think the gain is from less stop/start and the engine being warm (cold engines are much less efficient )

Data wrote: good ol 97 ron

I don't know about anywhere else, but 97 (or sometimes 98) is usually referred to as Super. 95 is regular.

I have never used 99 or higher and I am guessing that will be a lot more than the current 1.30 (1.38 for super) or so that is available in my neck of the woods. I wouldn't personally recommend going above 97/98. Not because I am an engineer, but cos I am tight.

Actually I think it isn't well known, but one of the major contributors to winning the Battle of Britain was that in the months before it all kicked off properly, the RAF upgraded the Merlin to use the newly available 100octane. Gave the Spit the performance boost it needed over the 109 and allowed the Hurri to close the gap substantially too.

Just thought I'd mention it.

well debatable then , although the higher octane fuel has more cleaner additives than the regular fuel, i have not gone this route as yet as i use standard unleaded with a concentrated cleaner bought my last bottle 17th june 2013 and only used half the bottle to date... its only 10ml for 3 gallons of petrol
its £7 delivered to treat 400 litres of fuel ... so i will probably still use this for now, as the j300 is at normal operating revs at 5000 rpm with the sprint filter letting in more air and the brisk plug burning the fuel/air mix at a rapid rate and the straight through exhaust is less restrictive.. so want to make sure its all burnt and the system and valves etc are kept clean SILVER HOOK PETROL TREATMENT & INJECTOR CLEANER
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CLEANS COMBUSTION CHAMBER, INTAKE MANIFOLD, VALVES AND FUEL INJECTORS

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Your engine is becoming clogged with unburnt fuel & carbon deposits resulting in decreased performance.
Silverhook Petrol CO2 Reducer is an advanced detergent additive containing CE+ patented technology which will give the interior
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In modern petrol engines treatment of deposits is often difficult.
Unlike conventional detergents this additive will remove deposits in the inlet manifold, inlets valves, combustion chambers in addition to fuel injectors.
CO" Reducer contains corrosion protection properties to increase engine durability leading to longer life of the fuel system.
In older vehicles this will also clean carburettors.

StephenC wrote:

Data wrote: good ol 97 ron

I don't know about anywhere else, but 97 (or sometimes 98) is usually referred to as Super. 95 is regular.

I have never used 99 or higher and I am guessing that will be a lot more than the current 1.30 (1.38 for super) or so that is available in my neck of the woods. I wouldn't personally recommend going above 97/98. Not because I am an engineer, but cos I am tight.

Stephen, thank you. That was a slip of the mind, not the finger on the keyboard. Yes I meant 95ron. Blimey, I'm gettin old! I'm tight too...it gets worse as you get older... I got myself into a situation with the 99ron in remote part of the country. The garage only had one pump that was working and all it had was the 99ron. Definitely don't use it in a Burgman. My bike didn't like it very much. I put the minimum amount in to get me home and didn't thrash it. After 60 miles or so I was able to stop at another garage and fuel up properly with 95ron. It made one helluva difference, back to it's old self very quickly after just a mile or so.

Ok I have just filled up the Max with Shell Nitro and will do that for the next few fill and see if it makes a difference. I have to say I am not convinced.

StephenC wrote:Try using super unleaded instead of the standard stuff too. In willing to bet that once you have used a couple of tanks that you will get maybe another 10% improvement.

Depends entirely on the engine, ignition and fuel injection systems design as to whether you will see any benefit.
If the thing is designed to run better on higher octane one would suspect that it would say so in the user manual?
If the manual does not recommend higher octane it is very unlikely there will be any benefit from using it.

It took at least 5 fill ups for me to notice how much smoother my TMax ran, I guess from clearing crud out, switching back with just one fill up of regular is very noticeable.