Wow, winter sucks: 71 mpg spring vs. 54 mpg winter in the Firefly/Metro, same trip

[MetroMPG]

Same trip in different seasons, with the biggest difference on the car being wheels/tires:

• 70.7 MPG (US) at 20C / 68F
• 53.8 MPG (US) at -15C / 5F

(... with just a 1 mph difference in average speed between the two trips. Yeah, the winter trip was the faster one.)

Winter's awesome! Ain't it?

This is for a 138 km (85 mi.) liesurely drive on secondary highways that passes through several small towns & one small/med city, average speed of 61 km/h (38 mph), maximum posted speed on the open sections of 80 km/h (50 mph).

Main driving techniques: driving with load; some engine-off coasting approaching stops/turns/longer descents; moderate speed (generally cruised on the open sections at ~75 km/h (47 mph) where traffic permitted).

Winter 185/60r14 Michelins (#3 best on my LRR list, below) are the biggest difference on the car. VS "all season" 155/80r13 Goodyear Invictas (#2 on the LRR list) which have better rolling resistance.



(From http://ecomodder.com/forum/showthrea...e92-19126.html )

And yes, you can mock me for not having wheel covers -- that hurt too. But I couldn't find the 14's that are hiding somewhere in the garage. And I know as soon as I make a set of coro covers, I'll trip over the other ones the next day.

[Daox]

YKYAEM if 54 mpg 'sucks'.

[NeilBlanchard]

The rolling resistance of snow and lumpy ice - and the slippage from same - are the biggest changes. And cold air is significantly higher drag! Better aero is even more critical in the winter.

[MetroMPG]

Originally Posted by Daox

YKYAEM if 54 mpg 'sucks'.

Yes! I blame the Insight! Since owning that car, 50-anything MPG feels like a giant rip-off.

=-=

Neil: good point -- there was some driving on ice & snow, but only a small portion of the total... under 5%. The rest was on bare/wet pavement.

Cold air is definitely worse for aero, but I wouldn't say it's massively worse at 45 mph cruising speed. Compare the aero power requirement @ 45 mph @ 20C (4.62 hp) vs. -10C (4.15 hp) in the aero & rr calculator (using the default vehicle settings):

4.15 hp @ 20C (68F) @ 45 mph
4.62 hp @ -10C (14F) @ 45 mph

So, ~10% more power consumed by aero loading through that temp difference. Estimated steady speed FE goes from 72 mpg to 66 mpg, all else being equal (which it wasn't).

(It was actually a bit colder on my drive: closer to -15C than -10C... which is the lower limit of the calculator.)

Just noticed: the temp change in the calculator should really be applied to CRR too, and it isn't -- it only affects the aero portion of the calcs.

[sheepdog 44]

Originally Posted by MetroMPG

Just noticed: the temp change in the calculator should really be applied to CRR too, and it isn't -- it only affects the aero portion of the calcs.

Yes, please please please! I don't know how the calculator is set up, but i whole heartedly volunteer to have a go at it. There are other helpful thing that could be added too.

http://ecomodder.com/forum/showthrea...tor-27824.html

[MetroMPG]

I'm ignoring that for now, sheepdog. (Nothing personal; it's my usual response when I've got too much on the go.)

[whatmaycome14]

I've noticed a big hit in my MPG since it got colder too! I can't wait for spring to come!!!

[aerohead]

I ran the CRX out of gas on the 30th.First time since 1991.
I damaged the sending unit siphoning the tank back in July and have relied on the odometer between fuel stops.
The cold,short commutes,traffic lights,and congestion all conspired to reduce range.After a 2-mile walk home,the neighbors were kind enough to run me to the station with a gas can,and back to the car.
So the distance between fuel stops has been revised downward accordingly.

[redneck]

MetroMPG
Wow, winter sucks: 71 mpg spring vs. 54 mpg winter in the Firefly/Metro, same trip

It takes a lot of miles to get the transmission gear oil and cv joints warmed up. On a recent trip of mine, it took approximately 80-100 miles (55mph) to get the trans. up to a decent temp. and it was only in the low to mid 20's. Driving leisurely at that temperature like you did will even take longer.

Which reminds me I need to update my fuel log.
(it's not good either)

>

[MetroMPG]

True. It would be a good idea to get a transmission heater on there as well.

Would I have used it? I'm embarrassed to say I brought an extension cord with me to plug in the car before I left, but it was -20C / -4F when I went to get the cord out of the car to plug it in, and it was so stiff and tangled (and I was so cold) that I said "screw it!" and went back inside.