Very common to get lower mileage during winter months. Refiners have to add lots and lots of additives to gas in order to comply with Fed regulations. None of the additives increase mileage.

 

Common knowledge that our motors make more power in cooler air. The air has more molecules per volume and so does the fuel. This results in a relatively bigger engine.

Yes, the metal in the motor also contracts as it gets cold but not to the same degree as the air.

If one were to be extremely judicious in their use of throttle they could retain the same mileage in cold weather as with warm. (except for the effect of those nasty but needed winter additives)

Most of us simply enjoy the increased power and use a little more fuel when it's cold out resulting in decreased mileage.


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It has to due with the refinery blending more butane to raise the vapor pressure of the gas. Our wonderful gov. has regs. the refinery follows each region of the country different time of the year. In the winter the reg is raised and the refinery adds butane which has less BTUs in it which means lower fuel mileage.

 

Add to all of the above, everything is cooler. The greater the difference between the ambient temperature and the item being cooled, the more efficient the cooling. Even the crank case oil doesn't get as hot, along with the transmission, chain case and wheel bearings, the oil and grease are all a bit thicker needing more power for a given speed. The "thicker air" also requires more power to push aside, it all adds up.

 

Most of your lost mileage is from the designer gas that our overlords in DC force us to use. In the winter they tailor the gas to evaporate more readily at low temps and to be more reactive in the catalyst exhaust systems. A small amount of your mileage loss is caused by cold air. It takes longer for the engine to warm up, so the system stays in open/loop/cold for a longer period of time.

Winter designer gas was meant to lower start up emissions on vehicles that were carb'ed and used chokes. It's of only marginal value to emissions reductions today, and the twice yearly switch over at the refineries adds about 30 cents to a gallon of gas at the refinery gate. That increases to about 55 cents at the pump, after retail profit and taxes are figured in. There is also some concern that the down stream addition of bio-fuels creates a product that does not meet the federal standards for seasonal motor fuel.

 

Really? Winter gas is different than Summer gas?
Man, I'm going to have to stock up on that Summer stuff before winter comes along and ruins my mileage with that rotten Winter gas.
Sheesh - winter gas. And here I was going along thinking I'd heard it all.

 

Very interesting thread. I have noticed a good dip in MPG the last few months. I just attributed it to "driving habits".

rkc

 

Roger - you've not heard of that...is it so hard to believe that refining it is different from winter to summer. They usually make up the excuse in the summer when gas goes up that they refine it differently so it costs more to produce...I can tell you for sure my mileage is worse in my truck right now (not using 4x4). Seems to me about 1.5 mpg less actually...

 

Roger - you've not heard of that...is it so hard to believe that refining it is different from winter to summer.

OK, I looked it up and there actually IS a difference. I stand humbly corrected.
Still doesn't convince me that it's the reason for lower fuel mileage. That's been going on all the way back to the mid 60's when I started driving and long before the EPA even existed.
We always wrote it off to colder temps causing longer warm-ups.

 

Your mileage in your cage will go down in the cold weather also. I'm not sure about the winter/summer gas thing but cold air is denser than warm air. Therefore more air is pulled in on the intake stroke with cold air. More fuel is added to maintain the proper air/fuel ratio and your mileage goes down.


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Summer vs winter gasoline

http://auto.howstuffworks.com/fuel-efficiency/fuel-consumption/summer-fuel1.htm

 

Don't forget you need to swap the summer air in the tires,to winter air also.
thats good for a couple mpg

 

S--t! forgot about that, thanks for reminding me. LOL.

 

colder air is more dense, makes a better burn

 

Still getting over 40 mpg. More important to just ride and not worry about it.

 

Im very confused now

So, always understood that the cooler=denser the charge of air entering the cylinder the higher the output.... Reason being the air will expand when ignited. This is why intercoolers exist.....
Living in the last century with my carb, lol, pretty sure it can't tell the density of the air passing through it's venturi, yet it definately produces a crisper throttle response when it's up to operating temp and cold outside.
Question is, can the sensors in an EFI bike compute the density of the air passing thru the intake? I really don't think so as we do not have MAFS on our bikes that I know of.... OK, just got it, the O2 sensors monitor the unburned fuel and adjust the mixture ....
Another question... If the air is denser when cold (a fact), and our carb has no way to tell?? Guess I know why it's crisper when cold, it must be leaner?
Wait a minute, if it's running leaner shouldn't it be getting better mileage/ Oh yeah, I am.....
Love my carb...
And yes, I have been drinking tonight lol...

 

Midwest Corn

Mine seems about the same... my wrist has the most noticeable effect.
That said, the winter addition of midwest corn farmer subsidies in the form of corn oil added (15% per gallon) really wags me out.... make cereal, furget puttin that power robbin CRAP in my fun fuel!!!