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anyone else fuel economy dropped slightly now the cold weather has drawn in? (northern hemisphere) temps are just about reaching 8degrees C here right now and i have noticed a small decrease in my MPG..

Mines holding around 130 mpg (was 141 first fill-up) so still excellent < both using litres in / trip miles. I've never been able to get near what I got to start with as it's gone down but stabilized, although it has been getting colder so that may be having an effect.
My rear tyre pressure was 8 psi under two weeks ago, so that in itself was not helping. The last reading is down a bit but I believe my next fill-up will show around 133.

Sorry, posted in error.

Absolutely goes down. I am always between 95-100 mpusg during the summer. Last fillup was down close to 90 as our temps have been 45-55 F, and I expect a bit more drop before Mantis goes for the long nap.

Anyone know why economy drops? It's been stated some fuel changes in composition during winter months as the additives change to cope with lower temps (in the UK Esso and others change twice a year - once for winter, back for summer) but are there other reasons why mpg drops when it's colder? I thought it was due to having to ride slower, stop/start more often and go slower due to poor visibility, wet roads, congested traffic in cities - is there more to it?

I used to work for a petroleum pipeline and there is a difference in regular unleaded gas from summer to winter. So it could be once the winter gas starts getting distributed to the filling stations you are seeing that drop. Looking at the dates in the graph seems about right.

PJDawgs wrote:I used to work for a petroleum pipeline and there is a difference in regular unleaded gas from summer to winter. So it could be once the winter gas starts getting distributed to the filling stations you are seeing that drop. Looking at the dates in the graph seems about right.

i know your in the US but i guess it could be the same for the UK as well.

The difference is mainly from a different mix in the winter fuel that is supplied but there are also physical reasons for a loss in efficiency. Colder air coming into the engine wastes more of the heat energy of the gas just to heat up the air during combustion. The thermal mass of the powertrain wastes more heat energy to get warmed up. The air density you are riding through is thicker. ect.

Colder air is thicker which is better (that's why you have intercoolers on turbo engines) - more air -> more oxygen -> You can use more fuel -> MORE POWER , but you need more energy to keep the engine temperature in the optimal range. And it takes more time to reach this temp. So you use more fuel for that.

wojtek_pl wrote:Colder air is thicker which is better

Better for max power. Worse for fuel economy.

Agree. You need more fuel if there's more oxygen or else the cylinders/Pistons etc get too hot coz the air fuel mix leans out that could foul spark plugs and cause pinging (worse case).

danieljw wrote:anyone else fuel economy dropped slightly now the cold weather has drawn in? (northern hemisphere) temps are just about reaching 8degrees C here right now and i have noticed a small decrease in my MPG..

Shot any more pix of your scoot and countryside which you could post?
Thanx, Fish

In mid Novemberr the petroleum distributors start pushing the winter blend through the pipeline. The winter blend makes cold starting easier and reduces emissions. Unfortunately it also reduces economy. If the winter blend were used in the summer it would increase the likelihood of vapor lock.