MPG

Top class fuel costs more at the pump but overall is cheaper than cheap unleaded. These bikes run very weak as standard especially at light throttle. So what, its saving fuel. This is true, but weak air/fuel mixture = very hot exhaust gas temperatures that can hammer the exhaust valves and seats.

Cheap fuel causes the spark timing to retard (avoids pre ignition - pinking). This further overheats the exhaust gas.

I personally want the ideal mixture but if that means it sometimes runs rich, the increased fuel bills will never amount to the costs of a dropped valve.

PS valves can fail - it happens. But I'd rather increase my odds of it not happening.

I followed my mate to Assen, he was on his HP4 - as it happened we needed to fill up at the same intervals which i found slightly interesting, although i don't know in terms of milage what the distance was... i tend to calculate "Smiles per Hour" because i get a lot more of them on the GS than i do Miles per Gallon.

Bendy toy said:

Top class fuel costs more at the pump but overall is cheaper than cheap unleaded. These bikes run very weak as standard especially at light throttle. So what, its saving fuel. This is true, but weak air/fuel mixture = very hot exhaust gas temperatures that can hammer the exhaust valves and seats.

Cheap fuel causes the spark timing to retard (avoids pre ignition - pinking). This further overheats the exhaust gas.

I personally want the ideal mixture but if that means it sometimes runs rich, the increased fuel bills will never amount to the costs of a dropped valve.

PS valves can fail - it happens. But I'd rather increase my odds of it not happening.

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Thanks for the heads up... (and apologies if it's off topic) i had to google it to find some more facts and found this -http://oldeloohuis.com/octane3.html i'll be looking more closely at the fuel i use in future.

That article about octane ratings and so on may have some relevance in a system where we are talking purely about the octane rating of a particular fuel. Unfortunately it falls flat on its face because today the very best fuels do not rely purely on the perceived octane rating, one has to take account of the chemical additives in the fuel which make it more efficient and better for the life of the engine. These fuel additives have no octane rating themselves but do make the fuel burn better and enable an engine to make more power. As an example last year Ferrari said that by far the biggest aid to the performance of the motors in their cars was the fuel supplied by Shell.
Given the choice of running standard unleaded fuel or the very best Shell V power fuel or other top grade fuel I would use the V power. You may not notice the difference but inspecting engine parts after a lifetime of use will show significant improvement with respect to deposit build up and corrosion within the engine... it is not all about power you are looking after your engine.

I know some of you guys will ridicule me but my bike ,like most others, sits in the garage for most of the winter. It doesnt use any fuel but still loses probably £5 a day on depreciation and we cant do anything about that. Never mind I dusted it down last week and reminded myself why I still keep it. Roll on summer!!.

Bendy toy said:

Ive had 340 from the GSA. It must have been running on fumes when I filled up. It took more than 34 litres to brim the tank.

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Jeez! makes you think...

stuartw said:

Jeez! makes you think...

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That was MPG not MPH of course

The stuff about posh fuels giving more power is never a simple issue. Some fuels have more energy per litre and a higher octane so they give better mpg than just the octane rating would suggest. I like to use Shell V-Power but Tesco Momentum 99 is defy better than BP or Esso 97. I've had Asda and Morrisons when desperate for fuel and the bike ran like the tyres were flat. Horrible stuff. That difference can't be just the octane rating - can it?

Octane rating makes the biggest difference because the engine can burnt it more efficiently - less heat thrown down the exhaust. The other benefits of posh fuels like cleaner burn and higher energy value (if it exists in practice) are further down the benefits scale.

Fuels like methanol have a very high octane value but low energy per litre. Diesel has a high energy per litre but very low octane rating. Getting a high octane fuel with high energy density is harder to achieve hence the price differences.

Edit
Cetane (self ignition quality) is another thing altogether & ignored by spark ignition engines.

MGJ said:

Has anyone ever got 300 miles out of a 2005 GS tank ? not GSA.

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Yesterday I ran my 2007 1200gs to 341 miles on a single brim filled tank. Its my daily 60 mile commute to work and back. Mostly motorway and dual carriageway. Google maps says my odometer is overreading by 6 miles in 100 so knock off 20 and that's 321 actual miles. Fuel strip said I had 4 miles worth left in the tank but it regularly lies to me so I carry a bit of emergency of gas in a can. I suspect it was less than 4. I do a steady 50 mph on the dual carriageways and the 6 miles a day of town riding at sub 35mph.

Not exciting riding but its a commute to work not a track day.

My 08 1200gsa ( which died of boredom circa 2016 ) did more than 500 ( indicated ) miles to a tank commuting to work on more than 1 occasion.

Regular unleaded gas in both.

Coming back from Italy during the French fuel strikes, I rode my GSA to tease every last drop gently out of the tank, accelerating slowly, short-shifting and coasting wherever possible instead of braking and with a self-imposed top speed of 60mph. Really boring riding but my mpg was showing 59 and range was showing over 500. Sadly I forgot to note the true mpg/distance per tank but its the best I have ever got from a 1200 boxer.