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Old 01-15-2013, 12:27 PM   #1 (permalink)
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Winter driving: Best way to keep those MPGs?

Hey gang,

Here in Idaho, we typically see winters that don't keep snow around long... usually stays between 20-40*F. This January, we've seen a lot of 0-25*F days. My home's heating bill is definitely proving the harsh times, but also, my last fillup was the 2nd lowest I have had with this car! 8-9MPG less than my average, I got ~35MPG (all city). All winter, I tried to drive it like I have been: Shifting at my estimated maximum BSFC recommneded 3.5K. I don't actually have a chart for my engine, on top of various modifications, but looking at other charts for similar engines, I made this my determined point (and tested various shift points with little/no difference) Regardless, Summer time weather had proven it to be fine, where I'm really seeing some suffering in this bitter chilled weather.

My intake is not pulling in warm air of any kind and my engine is not getting pre-warmed with any heater elements. I keep the car in a garage, but with the outside getting as cold as it's been, ~40*F seems to be the norm in my garage. I realize a few mods can easily make my car warmer and keep better mileage, but I wanted to make a thread on driving in conditions like winter offers. I bundle up and don't touch my heater at all on the way to work in the mornings to keep engine heat going as well as I can, plus, by the time I get to work, the engine barely hits 100*F anyways.

So after that grossly disappointing tank, I decided I need to experiment in these cold temps a bit. On my way to work, I decided to throw out my usual shift points and try going a bit lower. I shifted at 2K instead of 3.5K. Everything else I kept the same: coast to the stops, engine off completely instead of any idle (unless ~10-15 seconds or less of coasting/idle time), etc. Before, with the 3.5K shifts, I was seeing 35-40MPG at the end of my trip with my scangauge. With 2K shifts, I ended dead on 50.0MPG this morning. Outside temps I believe were 4-7*F and everything else remained roughly the same.

It's going to take more testing, but it looks like colder weather likes lower RPMs thus far.

So, what tips can you give to further increase in these cold times?

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Old 01-15-2013, 03:54 PM   #2 (permalink)
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3500 rpm shifts seem a bit high, even in a four cylinder. I've never shifted that high in normal driving in my 1.6L, 1.7L or 2.2L cars (I have a lot of cars, lol).

Shifting at 2K is probably good, but have you tried shifting even lower than that? I was surprised how low my cars will put up with, shifting the Probe as low as 5th at 30mph. Of course the Honda doesn't have enough low-end to pull this off.

On with general stuff...

It should go without saying that you should avoid snow and slush to improve MPG- if you've ever ridden a bicycle in these conditions you know all too well. Don't spin the wheels if you can help it; some icy spots may require starting out in second gear for less wheelspin.

Grille blocks, engine insulation (be careful) and warm air intakes help keep the engine warm and I'm told block heaters and frost plugs do wonders as well. I can't park inside so I need to run the defroster for five minutes on the way to work- it does increase warm-up time. Keeping frost off the window doesn't make it fog up less, either!

Make sure your tires are pumped up, as the colder air condenses and you get less tire pressure per weight than in the summer.

One thing many of us may not think of is clearing snow off the roof. While it's great for aero testing, it's bad for your drag (CdA)! Don't inadvertently increase your frontal area if you can help it.

That's all I've got for now
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Old 01-15-2013, 04:30 PM   #3 (permalink)
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Double check your air pressure.

Preheat your engine (it really can pay for it self even in your garage).

Think about not doing EOC. Your o2 sensor cools faster and to a lower temp in the bitter cold. It takes longer to warm it to operating temp, keeping you in open loop longer. This erodes some of the advantage that EOC gives you. It also lets your cabin cool, forcing you to bundle up more. Which makes you less comfortable and therefor a less efficient driver. Bumpstarting on compromised surfaces is also a hazard.

Slightly lower top speed. More air drag (from the denser cold air) and thicker goop in your transmission/differential, CV joints, wheel bearings, and your tires being colder and less pliable. The faster each gear tooth or bearing roller has to force oil or grease out of the way the more energy is required to do so.

Get winter tires, better traction means less slipping and sliding. Many compounds have very low rolling resistance. I was very impressed with the hankook I pikes I had on my civic year round.

Edit: What he said about your shift points. They seem high, especially when you consider thick cold oil.
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Old 01-15-2013, 06:19 PM   #4 (permalink)
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Temperatures have been near zero Fahrenheit for the last week or so. I drove my gasser pickup this morning because I still have some biodiesel in my VW tank that gelled last month and is still giving me an occasional issue.

Before the truck was warm, in the cold the difference in coasting speeds was shocking. I was slowing to a stop well in advance of lights, where before I was having to brake slightly. I guess the axle grease takes a while to lose it's friction.
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Old 01-17-2013, 01:34 PM   #5 (permalink)
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Quote:
Originally Posted by UFO View Post
Temperatures have been near zero Fahrenheit for the last week or so. I drove my gasser pickup this morning because I still have some biodiesel in my VW tank that gelled last month and is still giving me an occasional issue.

Before the truck was warm, in the cold the difference in coasting speeds was shocking. I was slowing to a stop well in advance of lights, where before I was having to brake slightly. I guess the axle grease takes a while to lose it's friction.
i never thought about the biodiesel gelling before, interesting
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Old 01-18-2013, 04:10 PM   #6 (permalink)
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I'd start with an oil pan heater, block heater and some 0w-XX oil!

You don't need to warm up for too long either. I can let my Focus idle for a day and it'll never come up to temperature.

Not only biodiesel, but diesel gels too. Diesel has it happen at a much lower temperature, though.
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Old 01-18-2013, 05:42 PM   #7 (permalink)
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^^^ Actually you don't need to "warm up" at all in a modern car. Just don't go racing around on a cold engine. In cold weather my '65 truck needs to warm up for a few minutes to avoid stalling but with EFI in my other cars that issue is gone. Just start up and drive.
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Old 01-20-2013, 07:34 PM   #8 (permalink)
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I park my car in the garage, which seems to never drop below 40F due to the hot water heater, furnace and attached wall. This means I don't have to defrost on my morning commute, and fluids start at a higher temp.

I have just installed a full lower grill block in addition to my taped off upper grill. This seems to have improved FE, but during the hour I was on the freeway the cooling fans cycled about once per minute. I'll need to open it up a little. Temps stay just right for my short 15min commute though, and having a fully blocked grill seems to keep the engine warmer than it normally would be after it sits for a while.
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Old 01-21-2013, 01:04 AM   #9 (permalink)
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Quote:
Originally Posted by UFO View Post
Temperatures have been near zero Fahrenheit for the last week or so. I drove my gasser pickup this morning because I still have some biodiesel in my VW tank that gelled last month and is still giving me an occasional issue.

Before the truck was warm, in the cold the difference in coasting speeds was shocking. I was slowing to a stop well in advance of lights, where before I was having to brake slightly. I guess the axle grease takes a while to lose it's friction.
This is interesting because on most vehicles, there is no oil cooler, no cooler for differential, and for manual trannys, no cooler there. By the same token there is no preheater for them either. With ambient temp differentials approaching a 100 degrees f between summer and winter in many parts of the usa, its a wonder mileage doesnt change more than it does. Here in central va i give up between 10 and 20% during the winter due to the above factors, not to mention the fact that winter fuel is more volatile and a gallon of winter gas wont go as far as a gallon of summer gas.

I would think a water jacket on each driveline component connected to the cooling system woul pay significant benefits in colder climates, especially with a coolant heater and circulating pump that you could plug in inside your garage

In the summer it would help keep temperatures at coolant temp and extend the driveline components life.
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Old 01-21-2013, 01:51 AM   #10 (permalink)
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As others have said ... No warmup. I get completely ready to drive, including making sure there are no cars to yield too, and turn the key and go. I also fabbed up a warm air intake but don't really know if it heps or not. I adjusted the intake location so that I get about a 20-30 deg increase in intake temps. I'd never run it except in the winter as the intake temps would be dangerously high if I got stuck in traffic.

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