Fuel Efficiency Drop
 

I have notice my efficiency drop from about 7.3 L/100km to 8.5 L/100km with the colder weather on the exact same daily commute. Has anyone else had their cars drop this bad? The only other change was i put winter tires on, but the first week they were on i still got 7.5 L/100km.

Well colder weather will have an impact. And it can be significant if the trip is not long enough to achieve full enough warmup to balance off the richer running when cold. Are your winter tires the same diameter? Some folks think the car can compensate for this somehow, but I have never seen an explanation of how it would do this?

That's about what I saw over the last year, summer average was ~ 8L/100km in the city, winter went to ~10-10.5L/100km once it got cold. I track every tank and I also noted that the dash fuel consumption reports roughly 0.4 to 0.5L/100km lower than the actual. And this has been consistent for every single tank I have put in it. So, you're likely doing even worse than you think unless you calculate the numbers yourself.

Winter blend gas is here bud. The specific blend of fuel at the same octane rating will have less energy per litre of fuel.

http://jalopnik.com/what-you-should-...g-i-1450089585

Yeah I started noticing that too on the BRZ. Same thing when I had my Civic, I tracked every tank for 4 years with the exact same trend.

Yep.

I figured all that. My tires are the same and I track every tank with an app on my phone. my Cobalt wasn't affected as bad, just wanted to make sure this was more or less normal. Thanks for the replies guys.

It's a combination of longer warm up times (less efficient while warming up), the different blend of gas, and typically slower commute time when roads are bad

Sent from my Nexus 4 using Tapatalk 4

The stock tires too are made for better fuel economy and putting on winters (in particular, but really any tire) will lower the fuel economy slightly (if you were running the stock summers).

That sucks. I hate being at the mercy of big corporations.

Higher density air due to it being colder means the matching and appropriate air/fuel ratio mixture must be compensated for accordingly.

More air, more fuel. Simple stoichiometric balance being maintained.

Yes, that is true. But due to the air being more dense you would actually require less throttle to accelerate the same. "The air being more dense" isn't the reason you burn more fuel. Longer warmup times + thicker oil on startup + winter gas + less efficient tires is your reason.

Air density is one of many reasons.

http://www.metrompg.com/posts/winter-mpg.htm

The only part related to air density in that link was aerodynamic drag. They generalized that aerodynamic drag increased 2% per 10 degrees f. It isn't anywhere near that simple, and can't be generalized that way. Speed would be a variable which throws that number out the window. Also the Source for that info was a Cummins engine website, likely referring to large transport vehicles.

I am not anywhere close to an expert in aerodynamics, or drag. I just did a quick search and posted that article as the first I found... Summed it up fairly well. With my limited knowledge, up until this year, I always thought it was just because I turned the heat on in my car in the winter!

I think the point was more that there is many little bits that have a cumulative effect on fuel economy. The air density was likely one of the least influential.

I would suspect blended fuel to be one of the top reasons for any drop so far. I never even knew about this until I saw this thread. Learn something new everyday. I've noticed a significant drop already (~7.5-10%), car in garage, traffic identical, no idling, tire pressure, and obviously no icy roads contributing to friction, etc.

PS: even though the source was from a Cummings engine website, the person writing it talks about the chart taken from a Honda civic hybrid, and talks about how it relates to his honda accord. And I'd have to agree with the numbers based on all cars i've owned, protege, celica, mazda6, escape, grand vitara, and now a 2014 mazda6.

There is a reason for the extra butane. Because butane boils at lower temperature it is increased in winter to assist with better starting at lower temperatures. Gasoline is made from a range of hydrocarbons that vary in density, boiling point and energy content. The range is tailored for the season. The energy released by burning the lighter molecules generates the heat to burn the heavier molecules. The heaviest part of gasoline boils below the initial boiling point of diesel fuel. While you may think that gasoline explodes in an instant with the firing of the spark plug the burn rate once the light ends are ignited is actually managaed by the progressive combustion from the lightest to heaviest parts. If this isn't managed correctly, you will notice it in vehicle performance.

So gasoline is always seasonally adjusted to optimize its performance. But there are trade offs.

Adding butane in winter isn't new at all and has been a fact since almost forever in the history of gasoline. Limiting it in summer to the degree it is today is newer and dates back to the early 1990's. Before that the only limitation was for performance reasons: too much could prompt vapour lock. Since then it has been further limited in summer for reduced evaporative emissions.

Interestingly butane(which can be in many forms) also has a pretty good octane number, but yes, also less density so less energy content.

So the extra is there for a good reason.

2 tanks of suspect "winter blend" gas: 8 L/100 km (AT)

Previous tanks of summer gas: 7.3 L/100 km (AT)

Almost 10% more fuel consumption over the same commute.

I honestly have garbage fuel efficiency because I cant hold back from revving her on corners and swirvy roads.
I can't hold back from revving her anywhere actually. I think I avg 13L/100k. :P

Wow 7.3L/100km?? Either you do a very high percentage of highway to city driving or drive like a granny lol

My commute to work is 90% highway on the QEW, average speed during rush hour is 85-100 km/h. Couple that with a tall 6th gear on AT = actually decent economy.

Haven't seen the winter gas hit here in the GTA yet.. still getting 600km's on a tank in my winter beater, once winter fuel hits I am lucky to hit 550kms (09 yaris)

I can get 7.3L/100 in the BRZ in the summer on the way to work (5:30am on the 401) but never on the way home...

You weren't talking about me, but I'll volunteer I do both. 81% highway driving, and at 90-95 km/h. The gas money is better in my pocket than theirs, plus everyone who goes by me gets a nice long look :)

7.3 isn't all that crazy. Cruise at 110km/hr going Calgary to Edmonton and back I averaged 6.2 through the whole tank, even playing around and going on some spirited cruises while there. Managed to hit 700kms to a tank and was pretty impressed.

All vehicles will take a fuel mileage hit when the temperature drops. Others here have already explained the reasons why. My 4-Runner goes down to around 17L/100km in winter :(

Update: Frosty mornings and idling have gotten me from 8 L/100 km to 8.5 L/100 km...

Wow! you guys are good! I'm doing 9.3 L/100km on manual! Although my daily commute consists of 10km round trip city driving to office...

~7.9-8L/100km now...
Had been doing better (7.8) in the summer and when I first got the car.

I have bad gas. And winter blend sucks too.