As has been, and is currently being, discussed ad infinitum fuel economy drops in the colder months. I've been curious to see how my 'stock' FIT is effected by cold weather.

This last tank of regular gas has been through some bitter cold days in my part of the world and the on-board MPG's have shown a 34-35 average. On yesterday's fill-up I ran the numbers and was surprised to see 37.26 come out. To dispel the naysayers I used the same station and the same pump.

My first question is how do others see the winter temps effect their mileage, both on-board and pump computed?

Now I'm hoping not to turn this into a one-sided super tech discussion on engine tuning techniques. I really am not interested in any of that. Please, impressive as it is, keep that to an appropriate performance section - I'm talking stock set-up as, I would guess, the vast majority of owners have.

My 'guess' is that the on-board might be seeing things differently due to the colder air intake running things richer, but some how not reflecting the real world values...

Correct, it's a guess, so my second question is how are the on-board MPGs calculated?

My 2010 Sport MT has always given an accurate comparison between the two ways of calculating, but now - in the cold of winter - I'm seeing a difference.

Hopefully a few more tank-fulls and feedback from others will help explain....

Happy Holidays to All

K_C_

 

I can tell you that my calculator came up with 29.2 mpg and the OBC said 29.3 mpg on my last fill up, so that time the OBC was pretty much spot on and you know what, its pretty close most of the time. I will say this, when I figure my mileage out, I put the mileage in complete, to the tenth as well as the amount of gallons pumped in, i.e. 157.8 miles and 4.788 gallons (this is a made up number)

I know this, when the highs were in the mid teens, my mileage was barely 23 mpg and now its close to 30 mpg with the temps around 32.

 

I live in Iowa and I could go on and on about how bad the winters are...my 2009 Sport AT suffers in MPG during the winter months.

During other times of the year when we have good weather, I average a combined 39-41 mpg. Now, with the temps constantly very low, I average a combined 32-33 mpg.

 

In Wisconsin, 2009 Sport MT. Tracking this over the past year in summer I'm consistently at 37-40mpg (I use GasCubby), and in the cold/snow 32-33mpg. I don't see the computer being more or less accurate in summer or winter. The computer still estimates a few % high for me even with the updated sw. Good luck.

 

Just look at the monthly graph in the fuelly link in my sig and you can see easily how much mine changes with the cold. I'm up at 37-38 routinely in the summer, and down around 32-33 in the winter.

 

My OBC has showed anywhere from 20-29 mpg this winter, crazy! Lately, I've been getting a little over 29 mpg using the "old school" method. I wonder if I'm actually getting a gallon when I pump a gallon, someone said something about this in the other thread about grade of gas, makes me wonder

 

The cold weather does a lot of things that effect mileage figures but running rich should only be occurring during warm up... There is more fuel going into the air fuel mixture due to the higher oxygen content of cold air but this only means you need less throttle to make power... Consider that the lubricating oils and ATF on cars equipped with automatic transmissions is going to be thicker and require more power being used to circulate and if you are using the defroster the A/C compressor is running and using power also unless you have disconnected the wire that bridges from the A/C switch to the defrost switch... Also you are using your lights more often and if using snow tires are increasing rotating mass and rolling resistance.... Disconnecting the A/C to defrost switch wire, using winter weight oil, blocking the flow of air through the radiator, start driving within a few seconds of starting the engine and waiting until the cold light has gone out and getting what you need to get done in one trip instead of many are ways to use less fuel.

 

I wonder too, if you get what you paid. Also the quality is worse from a few years ago. I remember getting 38 mpg in the winter of 2005 in my 2004 civic. Because ethanol is splashed in, its very inconsistent. Thats another reason to use premium.

 

okay, please clarify that one.

Do you mean the defrost option on the vent knob? ie, front windshield vents... or the defrost button that activates the heating wires on the rear windows?

I wonder that too on occasion.

 

I find the same thing, I use "My Mile Marker" since 11/09, fill up with Exxon prem. for the most part and it's all over the place from 20 to 36 ( I know this is somewhat do to filling up all the way up to the neck and other times just the second click) I have an average of 29.2 today and it has been going down since October. But I do drive her hard, so this to takes the MPG's down. Still love the lil' rascel though.

 

I cant explain the inconsistent gas mileage. Until 2009 I would get over 35 mpg every tank in the winter in my Fit, The last winter really brought down the mpg 30-32 and this year in my new car 29-30 mpg in the extreme cold and granted it warmed up a bit and its up, but I am still disappointed. They cheapen the gas and charge more, or you dont get what you paid for. I am the one that wrote you dont get what you paid for. I filled a gallon gas can after filling my car. It holds 1 gallon plus 4 oz. There was about 4-5 oz still in there and I put and 8oz bottle of oil and then filled up an still put in over a gallon. So if you pay for 10 oz per gallon in a 10 gallon tank its almost a gallon that you did not get. Thats a 2.5 mpg loss per gallon. Any ways I have noticed the decrease and inconsistent mpg for years now. My wife car gets a little better than the van it replaced.

 

the defrost option on the dial. it can be removed so that when you do use the defrost mode you dont have the A/C compressor running.

Im skewed on my MPGS, cause I use my remote start more often in the winter (so more idle time). however during normal cruising (i do 80/20 highway/city) i still get 30-32 mpgs which is well in my average.

my big problem is when i do local, i fail miserably to low 20s

 

I apologize for not answering that question Goobers I saw it and was going to respond but forgot to.... With the wire disconnected you can still turn on the A/C to dry out the air more if it is necessary.

 

No worries. It's not like I was sitting on here staring at the screen waiting for you to answer (cause if I was, I ain't admitting it!). lol

I had an idea, but I just wasn't sure.

I try not to use the A/C much (if at all)... but I don't mind it the few times I do (windshield vent). Use it, get the job done, switch back.

 

Well thins winter fuel economy thing has me confused. I can understand the principal, but the real world has got me.

First off, I'm dismissing the defugalty in the numbers of my original post between my computed MPG and the on-board MPG. I'm thinking user error.

However, over the Christmas holiday I was again up to northern Maine. I'm driving US1 from Waldoboro up to Bangor - it's 28d and falling and I'm seeing 38MPG on board. After a day of temps in the teens and shoveling a NE blizzard I prepare to head south and fill up the tank. 37.5MPG by the numbers.

All I can deduce from this is that 'most' of that driving was long-haul not stop and go. Once it started snowing we walked if we went anywhere at all. It is certainly the short trips that kill the MPG's and in the cold months it sure hits them harder.

huisj has recorded his numbers and I'm expecting to see the same this first winter.

As far as the AC and the defrost goes, I don't worry about it. My last Cadillac did the same thing and it bothered me at first, but I soon realized that the defrost efficiency was so much better it's well worth it. I'm always cringing when I see a car go by with the inside windows all fogged up - really disgusts me when there's no reason to drive around like that with today's cars being as they are. Phew - breathing all that... - yuck.

My 67 Beetle needed an ice scrapper on the inside of the windows in the winter and all that would clear them of the summer condensation was one of my little brothers diapers. To this day I keep a few cotton diapers around - and you know what? My brother doesn't even miss them!

 

I typically get 4-5 MPG less during winters, mostly due to others slowing down and jamming up due to minimal rain.
Due to winter traffic conditions, I shift and accelerate frequently...on the freeway...despite opening and closing 3 sec gaps. 91 octane seems to help alleviate the acceleration losses to some degree.

The ECU is likely integrating or summing injector on-times (should be mostly linear at the engine loads I'm demanding) or possibly the fuel pump (unlikely).
It does not seem to be as accurate with increased engine-braking. Est-MPG is ~+5-10% more than calc-MPG with much eng-braking, vs. +0-5% with less eng-braking. That could be other variables like traffic. Note, the Fuel Injection calc was reprogrammed and went from the +14.5% avg (~+10-20%) to +4.4% avg currently.

 

Here is a link to warming up in the winter for as long as it lasts. Eight Facts About Warming Up Your Car in Winter- Yahoo! Autos Article Page

 

Good list, however, when temps are sub-zero I would suggest a 5min warm-up before driving off, assuming you can get it started in the first place. I spent a long weekend in Lake Placid, NY once because of a week of -20F daytime temps and cars simply refused to start, and when they did it was obvious that the internals were in serious denial, ouch. I was driving a '74 Audi Fox and the only wat to get fuel to the cylinders was to pour cold water over the carb to thaw it out. Couldn't use hot water 'cause that temp change would have broken something for sure and there really wasn't a need. I was looking at a 70 delta temp anyway.........

World Cup ski jumping was canceled due to extreme cold that weekend.

 

Yea I agree with a little longer warm up to, I guess they never had to drive with ice on the window that takes at least 5 minutes to defrost.

 

Knock on wood never had a problem starting a car with in the 5 years. -20 is the limit on how cold a Honda would start with out a jump. Never heard of hot water over the carb but 25 years ago a friend had a Le-mans and it took about 5 hours to start with jumping. Once it started and got winter gas no problems. That car is still running. I miss those days.