Misc winter FE thoughts...

[DracoFelis]

Various people have mentioned/observed that FE tends to go down in the winter. And indeed, my best tankfuls have been in the heat of the summer. Which got me to thinking of some of the things that might be going on, and what we may be able to do about it. These are just my thoughts, and they aren't necessarily correct (so feel free to comment on them). However, they all seem to make sense, as least at first glance....

Air shrinks when it gets cold, and too low of a tire pressure hurts FW. And so, (as another GasSavers poster observed) we will naturally "lose air pressure" (even if the seals were perfect) simply because of the lowering outside temp. So if we aren't careful to "top off our tires", we will be running with lower pressure (and therefore lower FE).

The obvious "fix" for this, is to keep the tire pressure up. However, checking/filling tires can be a PITA when it is cold outside...

Colder engines tend to run "richer", and therefore use more gas. And in the winter, the engine will start off colder AND generally take longer to warm up. And unless you make a lot of long trips, this can be significant.

One thing I've done to help in this area, is to switch to a full "grill block" for the winter (even with the grill fully blocked, there is still air/cooling from under the car). IMHO the "grill block" is something of a win-win in the winter, as it not only helps the car heat up faster, but also helps with the front end aerodynamics. And with the colder air out, I'm not too concerned about the grill block causing the engine to overheat...

NOTE: I already noticed that the full grill block is helping. While I'm not up to my summer maximums right now, I am doing better than I was for the tank or three before that. And the car just feels like it "gets in the (FE) zone" quicker, with the grill block in place (which makes sense, as the engine should warm up faster)...

Many cars get their in cabin heat from the car's "cooling system". For example, my CRX has the car's heater plumbed into the car's cooling system. And that means that if you use your heater too much (or too quickly) the car engine might cool down "too much" (or take that much longer to warm up), resulting in the lower FE of the "cold engine" (above). I have actually noticed this effect in my CRX, when I first observed that turning up the cabin temp (not raising the blower speed, but just adjusting the temp) actually caused noticeable "drag". I later discovered that the drag was much less (and sometimes even went the other way, resulting in less drag) when the car had already warmed up. What I eventually concluded was happening, is that the "heater" causes extra cooling on the engine, with the greater the "heat" the more the engine cooling. And when the engine was already somewhat "cold" this caused the additional drag of a "cold engine" (but if/when the engine was very warmed up already, this additional cooling was sometimes even helpful).

About the only "fix" for this, is to either balance your needs or cabin heat against the needs of the engine, or convert the car into getting cabin heat from somewhere other then the engine (the tail pipe, perhaps?). Me, I just keep in mind this effect, and try to adjust the temp accordingly (for example, trying to make minimum use of the heat when the engine is first heating up).

You often use more electricity in the winter. Simply put, the "accessories" are more likely to be needed/used. And has already been discussed in this forum, more electrical use means lower FE. For example, you might use the rear-window defogger. Or maybe you have the heater blower on more. And lets not forget about having to use the headlights more when you are driving, due to the shorter daylight time in the winter.

There is only so much you can do in this area, as you really do have more of a need to use "power hungry" accessories. But the basics can still be done (such as not turning on electrical devices you don't need to use). And it never hurts to convert to more energy efficient car systems (for example, I've converted a lot of car lighting to energy efficient LEDs).

Cold tends to lower the efficiency of batteries. And this little fact probably makes the electrical issue (above) worse than it might otherwise be...

I suppose you could probably get a heater for your car battery, but it seems a bit "overkill". And if that heater was run off the car's electrical systems, it would probably even be counter-productive. About the only thing that really makes sense in this area, is to keep the car in a (warmer than the outside) garage, when that is feasible.

Car fluids flow less well when cold. And depending upon the fluid (and how much heat it gets from the engine), this can get in your way (FE wise) even after the engine is supposedly "up to temp".

I think this is one good reason for high quality "low temp" fluids in the car. This won't solve the problem, but it can lower the effects of the problem. For example, I've started mixing a little (about 1 qt) 0w20 full synthetic oil (the lower the number BEFORE the w, the better the cold temp efficiency), into my oil mix (which is still largely made up of 5w30 full synthetic oil). And I'm also looking at possibly going to 0w30 (with a little 0w20 added) "year round". And I also recently redid my radiator fluid, with fresh "high quality" (G-05 type) radiator fluid.

And anything that keeps the car warmer, is likely to help in this area. For example, if you have a garage, park in it. The "grill block" (mentioned above) probably also helps (keeps a little more heat in the engine compartment). And even a "block heater" may be an option for some.



Anyway, those are just a few thoughts I came up with about winter driving and FE. Anyone care to comment and/or add your own thoughts?

[thisisntjared]

the main reason:
the winter blend of gas sucks

[DRW]

Colder air is also more dense, so the car has thicker air to push through.
Thicker/colder fluids are not limited to the engine. The transmission takes longer to warm up. There is grease in the wheel bearings and axle CV joints that might not ever warm up.

[striegel]

Originally Posted by thisisntjared

the main reason:
the winter blend of gas sucks

So right! If every gallon has more stuff in it that is NOT gasoline, it cannot contain as much energy.

Regardless of the temperature, the drop in fuel mileage tracks perfectly with the introduction of the winter blend.

[rh77]

Also...

* Higher rolling resistance on cold roads (or snow/sleet/ice/slush)
* Also some vehicles don't like cold IATs for economy
* Even at full coolant operating temps, the Torque Converter is harder to engage in cold temps

RH77

[Peakster]

Originally Posted by thisisntjared

the main reason:
the winter blend of gas sucks

I think someone should do an A-B-A experiment using winter and summer gasoline. Maybe get one of those trucks that have 2 separate gas tanks. If it turns out that summer and winter gasoline have very little difference in vehicle FE, I'd buy $2,000 worth of gas in winter and bypass the big price surges in the summer months .

[rh77]

If I'm not mistaken (someone correct me if I'm wrong)...

Winter blends and Summer blends are now 10% Ethanol -- effectively meaning that there is no change in blends during the year as MTBE has been phased-out. This may be region-specific.

RH77

[zpiloto]

Originally Posted by Peakster

I think someone should do an A-B-A experiment using winter and summer gasoline. Maybe get one of those trucks that have 2 separate gas tanks. If it turns out that summer and winter gasoline have very little difference in vehicle FE, I'd buy $2,000 worth of gas in winter and bypass the big price surges in the summer months .

Not to start the discussion on ethonal again but I Think E10 gets a bad rap. I think the main difference in FE between summer and winter is the effects of the cold mention above and not the fuel. If you take a 1-2% hit in FE is it worth the GHG reduction? YMMV
http://www.gassavers.org/showthread.php?t=1863

Hello Striegel, welcome to the site. If you get a chance introduce yourself on the introduction forum and tell us about the blue box. There is another Xb driver here, yall can compair notes.

[diamondlarry]

In the past I have looked into the "heater control" theory of leaving it on cold with the blower off until the engine is warm. The info I found said the engine warms up quickly enough when the heater blower is off that the position of the heater control doesn't make a material difference. I believe that to be true. The heater core is a heat exchanger and if there is minimal/no air flowing through, it isn't losing much heat. So in the winter I leave my heater control full-on hot but do not use the blower until I see the temp gauge move up a bit or, depending on how foggy/frosty the windshield is, when I stick my hand up to the defroster and feel discernable heat. In fact I usually regulate cabin heat with only the blower setting, trying to use blower off whenever possible.

I think you're right. The last few cars I've had didn't actually have a heater control valve, but a door/flipper that regulated the air flow accross the heater core. Back before I wised up a got a more fuel efficient vehicle,( I had a Durango- no hate mail please ) I left the heater on cold and popped the hood and checked both heater hoses after the engine had warmed up and found both of them warm. My Saturn is the same way. Something I like about the Saturn is that it doesn't appear to engage the A/C compressor when you run the de-froster. The engine doesn't sound like it's laboring any more and the SG doesn't show any difference in FE/load between de-frost on or off.

Because I don't sit and idle for warm-up I go very slowly and carefully until the temp gauge starts to climb. Even though I scrape the windows off there can be a fog/frost issue in that period between leaving the driveway and having heat available for the defrost. My solution has been to leave the driver's window cracked open just a tiny little bit in the evening when I park so the window doesn't freeze shut. Then in the morning when I go I open it a bit further and try to do all my breathing towards that window. I have even gone so far on the super bitter cold days as to only close the driver's door to the first click for the first mile or so. If I don't vent, all that breath fogs up the windshield. I know it sounds pretty stupid but that really makes a difference. You learn tricks like this from having Corvairs and air-cooled VW's in -40F winters!

Thanks for the tip! I park my car in a garage so I don't have to worry about scraping the windows but fogged up windows still become an issue within 1/2-3/4 mile of leaving the garage. My dad drove both of those cars you mentioned but I must have been too young to have picked up on that great tip.

[swng]

Apart from all the above, imho, people eat more, carry more (e.g. rain/snow gears) and wear more when the weather is cold, thus adding loads to their cars, which hurt their F.E..