Seems like this time of year, early winter in Michigan, the available fuel becomes the "winter blend".   Several of my friends have complained recently about a decrease in gas mileage so I did an alcohol test and was surprised to find only 7.7% alcohol in regular pump gas. Just sharing the information..........................

64F100 57FAIRLANE500

What the explanation for decreased gas mileage? I know that dry, cool, dense air is good for performance. Humidity, not so much. could your winter weather be more responsible than the winter gas? Surely it takes considerably longer to reach normal operating temperature, during which more gas is consumed. 

I can’t explain gas mileage, but “winter” blend is a Reid vapor pressure measurement IIRC. I do know filling a car late fall and driving it on a warm spring day can have a vapor lock problem show up. Fresh “summer” fuel and it goes away. I’d suspect it has something to do with vaporization while driving. Colder starts are always hard on gas mileage, even in modern EFI cars with faster warm up cycles.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

All good and true points. The biggest cause of poor winter fuel economy is more than likely a result of the "remote start" feature - very popular here in the northern states.   It's amazing to see so often, vehicles parked with engine running and no one in the vehicle. This is not a scientific study by any means. FWIW, 2 of us drive a several hundred mile trip about once every month as we have been doing for many years so that may take some of the winter variables out of the picture.  We seem to complain about mileage generally around the same time and that can be other than winter. There are a few of us that calculate fuel burn religiously comparing notes when there's an unexplained change.  I'm not a refinery engineer but I have an idea the reformulated winter blend may change the vapor pressure, specific gravity and/or other properties of the fuel affecting btu content.  I "knew" there was going to be an unusually high alcohol content but was quite surprised to find that that was not the case, in this instance.  Fuel has often been discussed here and it's always interesting to hear the results from someone testing it. Kind of a reality check on the refinery. 

64F100 57FAIRLANE500

HEAR IN CANADA(BC,WEST COAST} SUMER FUEL HAS ETHENOL ADED FOR SUPOSED CLEANER BURN.WINTER FUEL IT IS REMOVED. I HAVE ISUES WITH RUN ON AFTER IGN OFF. IF I SWITH TO MID GRAD IT ELIMINATES THE RUNON. MY ENGINE IS A HEALTHEY 292 IN A 1949 MERC 1/2 TN.  

The 10% on pump is the maximum it can have blended ,but it could be lower. Alcohol will lean the mixture.

I work for a rental car agency and drive cars to and from the agency. I have noticed that if a car is left idling for any lengthy time the fuel milage will drop. For example a car that idles for about 20 minutes that has a fuel mileage average of 16 mpg will drop down to 15.7. It takes several 3 mile trips back and forth before the mileage number start to change. I have no idea how this affects long term usage just an observation of something I've noticed. Of course fuel mixture is changed seasonally but we don't idle cars in the summer months for long. The warming up has an impact on mileage for sure.

Y's guys rule!
Looking for McCullouch VS57 brackets and parts. Also looking for 28 Chrysler series 72 parts. And early Hemi parts.

MoonShadow, 292 w/McCulloch, 28 Chrysler Roadster, 354 Hemi)
Manchester, New Hampshire

While the vehicle sits in one place idling, it's getting 0 miles per gallon. The totalizer is not recording any distance but the engine is still taking fuel out of the tank against the 16 mpg, as in your example. 

64F100 57FAIRLANE500

Another issue that isn't usually mentioned is that along with being corrosive, Ethenol draws "moisture"..That's why all in all its a bad product for older vehicles!  


Paul