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Cooler weather=lower mpg???

1K views 10 replies 9 participants last post by  Philthy 
#1 ·
So this summer I was getting nearly 40mpg. Now the cooler weather hits and I can barely get 25-30. Granted I've gotten more comfortable on this VRSCDX of mine but dropping 10-15mpg? It's an 07' with 5200 miles on it. Any O2 sensors on this thing? Any thoughts would be a great help...
 
#2 ·
FWIW: My '04 runs stronger in cool weather, so I tend to twist the throttle more, leading to worse mileage!
In the Northeast we also have Oxygenated Gas, in the colder months, which leads to poor mileage.
 
#7 ·
Cold air influences a lot of things. Oil is thicker robbing some power, iat richens the mixture and short trips keeps the engine in rich mode longer. That along with winter grade fuel with ethenol all add up to less milage. My cars milage takes a big dump during winter also.
Ron
 
#9 ·
Richness of mixture is affected by coolant temperature. The colder the coolant the richer the mixture. Winter blend fuels are more volatile than summer blends and have more ethanol, reducing fuel mileage some more. I see a 5-8 mpg drop in mlieage during the winter months on the V-Rods and the fuel injected BMWs, but not on the carbureted R-80G/S.
 
#10 ·
Yeah, I'm betting it's the winter blend gas. Around here they have 10% ethanol year-round, and I can usually average 39-40 mpg (I'm usually a pretty mellow rider). This year when I went to Sturgis my mileage jumped to 45-47 mpg. I'm sure part of it is riding with those slow air-heads too though. Got back home and it went right back to 40 mpg. Weather very similar both places, so I think it's gas more than the weather, for me at least.
 
#11 ·
I'm not sure the degree to which coolant temperature affects the lenght of time the fuel injector is open, or "pulse width", but on my fuel injected BMWs with liquid cooling, the coolant temperature can lengthen or shorten the pulse width by up to 40% depending on temperature. It has a major effect on fuel mileage beyond the effect of winter gas.

The fuel mileage of my Street Rod tracks that of the K-100RS quite closely winter to summer, while the fuel mileage of the R-80G/S, which is carbureted, does not change appreciably. I have to attribute the decrease in mileage to colder temps and colder coolant temperatures more than the change in fuel blend.
 
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