MPG drop? What could it be?

[axy]

1) Winter blended fuel of the same rafinery should have exactly the same caloric value as summer blended fuel. The difference is in additional infusion of RVP additives allowing better evaporation of the fuel under cold conditions. Winter and summer blended fuel willl, when burned, provide the same energy output while winter fuel will smoke a bit more.

2) True, so consumption should be higher on short runs with cold engine and marginally higher during long runs.

3) Marginally important, attributing no more than 0.2-0.5 % to the total gasoline consumption, translating into 25 grams of fuel more in case of underinflation / 100 km for scooters.

4) Oil viscosity is discussed ad nauseam on all automotive forums and still poorly understood. 10W-40 oil usually used in Kymcos should meet SAE J300 standard both for 10W and 40W. This means the same properties (cold cranking and cold pumping viscosity) at - 35 C and 100/150 C. So, the viscosity is not an issue for winter consumption.

5) Very true.

What is most important and usually is not mentioned is the single fact that causes higher winter consumption.
Air is more dense and more air can be packed into single stroke of the engine.
This inevitably causes need for more fuel.

I have now calculated that air is 15 % more dense on a sea level at - 10 C compared to + 30 C.
You will notice that scooters consume roughly 15 % more at -10 C compared to +30 C too.

I like science and facts, it shows, doesn`t it?  

[zombie]

Now there is something to sink your teeth into... I have now calculated that air is 15 % more dense on a sea level at - 10 C compared to + 30 C.
You will notice that scooters consume roughly 15 % more at -10 C compared to +30 C too.

I like science and facts, it shows, doesn`t it?  How did you figure that? I'm not being a wise guy this time. That would be the answer to his question.

[Cortez]

1) Winter blended fuel of the same rafinery should have exactly the same caloric value as summer blended fuel. The difference is in additional infusion of RVP additives allowing better evaporation of the fuel under cold conditions. Winter and summer blended fuel willl, when burned, provide the same energy output while winter fuel will smoke a bit more.

2) True, so consumption should be higher on short runs with cold engine and marginally higher during long runs.

3) Marginally important, attributing no more than 0.2-0.5 % to the total gasoline consumption, translating into 25 grams of fuel more in case of underinflation / 100 km for scooters.

4) Oil viscosity is discussed ad nauseam on all automotive forums and still poorly understood. 10W-40 oil usually used in Kymcos should meet SAE J300 standard both for 10W and 40W. This means the same properties (cold cranking and cold pumping viscosity) at - 35 C and 100/150 C. So, the viscosity is not an issue for winter consumption.

5) Very true.

What is most important and usually is not mentioned is the single fact that causes higher winter consumption.
Air is more dense and more air can be packed into single stroke of the engine.
This inevitably causes need for more fuel.

I have now calculated that air is 15 % more dense on a sea level at - 10 C compared to + 30 C.
You will notice that scooters consume roughly 15 % more at -10 C compared to +30 C too.

I like science and facts, it shows, doesn`t it?  

I'll never post anything about fuel consumption again with you around.
 

[axy]

Now there is something to sink your teeth into... I have now calculated that air is 15 % more dense on a sea level at - 10 C compared to + 30 C.
You will notice that scooters consume roughly 15 % more at -10 C compared to +30 C too.

I like science and facts, it shows, doesn`t it?  How did you figure that? I'm not being a wise guy this time. That would be the answer to his question.

Quote is messed up here...

There are online calculators of air density. Also, there are two other MAJOR variables: altitude AND air moisture, all seriously affecting power output of the engine.
I have decided to disregard them, in fact, to keep them the same and change only temperature.

In fact, as you probably know, scoots with carbs are set out of the factory to be running a bit too rich during the summer and due to denser air they are probably running "just about right" during winter time.

For hyper-optimization, we should even change pilot/main jets for summer and winter conditions.


@Cortez: I am merely a novice, YOU are the real vehicle consumption guru!

[Cortez]

@Cortez: I am merely a novice, YOU are the real vehicle consumption guru!

Aww, you're too kind!
 

[zombie]

"For hyper-optimization, we should even change pilot/main jets for summer and winter conditions."     Most of the time (1) step colder on the spark plug will correct this. Lean burns hotter so a colder plug will dissipate some of the extra heat