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?