[baluundertaker]

While the engine does seem smoother, i have observed primarily a drop in fuel efficiency :(

Am currently in northern US and temperatures are currently consistently -10 or -15 C.

And also average speed is around 70- 80 mph ( 110 -130 kph)

I was actually trying to apply all science i knew while doing long drive last weekend and came to the conclusion that fuel efficiency has to drop due to heavier and denser air which reduces aerodynamic efficiency of the car.

And today i see an article that says efficiency has improved for everyone. What irony !!

May be because i live in bangalore (when in india) with very moderate temperature changes, that i have never observed significant changes in fuel efficiency from summer/winter before though i regularly check efficiency each time i fuel (kind of addictive habit of mine)

[dkcrpl]

Today itself i got surprised when i calculated my last filling average. it was crossing 17 instead of usual 15plus. I thought "shayad petrol pump owner sudhar gaya hai" but now i know the real reason.

[ghodlur]

Over the past 3 refuels, I have covered a distance of 1550 kms for a petrol filling of 103 lts giving me an unheard avg of 15KMPL for my Fiesta.

Go Fida.

[buz]

Well. For whatever it is worth, my 6.5 yrs old Corsa gave me an FE of ~14 kmpl over the highways during the final week of Dec while driving through South India. But then, I hardly make the 7.5 kmpl cut in Mumbai city driving. So, highway + weather did augur well for me. Could not go through the entire thread but, would like to ask GTO - is it just denser air that is the reason or is it the generic theory of the carnot cycle that predicts higher efficiency in heat engines basis larger difference in fluid (in this case, burnt fuel) temperature and ambient temperature.

[Shan2nu]

While the engine does seem smoother, i have observed primarily a drop in fuel efficiency :(

Am currently in northern US and temperatures are currently consistently -10 or -15 C.

Have you taken tyre pressure into account? While a temp drop might get you denser air/fuel, it can also affect the tyre pressure, especially under such extreme conditions.

So next time, make sure you check the pressure just before you go on a long drive and see if that helps.

Shan2nu

[anantnehru]

My SX4 with the CAI is rocketing every time I floor it! Best was last night around Vasant Kunj where my car temp gauge was showing 6deg Celsius. Absolutely brilliant feeling!!

[baluundertaker]

Have you taken tyre pressure into account? While a temp drop might get you denser air/fuel, it can also affect the tyre pressure, especially under such extreme conditions.

So next time, make sure you check the pressure just before you go on a long drive and see if that helps.

Shan2nu

I did check the tire pressures as it was a planned long drive. But i kept it normal as i used to do before. (32 psi) . Is there a reason to increase/decrease tire pressure in cold temperatures ?

While travelling to sub-zero temp areas what are the steps to be taken? Any advices? Im planning a Fagu trip shortly via Delhi on a friends Swift Diesel.

For eg: Any change to the coolant/oil?

Yes - You are supposed to use a lighter/less viscous oil if you are going drive consistently in sub-zero temperatures so that oil flows and lubricates the engine more easily. I have never owned a diesel car, so cant suggest on particular spec oil.

[kiku007]

FE has definetly gone up for my Fiesta Petrol in Chennai! I'm pleasantly surpirsed

[bluevolt]

yes the engine feels more smoother, but the engine takes time to warm up and the idling speed is higher than what it is during summers and FE is higher also because of no AC usage.

[figo_mba]

Now its been 5days since the onset of monsoons in Kerala.
I own a Figo diesel and my mileage was 18.4kmpl. I am doing a regular office to home shuttle.
Since the time I return from office and I go to office are similar I can say that the traffic is almost same.

I have noticed my mileage has suddenly improved to 20kmpl (20.6kmpl)
The only difference i see is the onset of monsoons.
So the question is How is it that the mileage suddenly improved?

And yes I use 100% AC even during rains

[clevermax]

The onset of rains should have the opposite effect on your mileage. More rains -> more traffic jams -> decreased mileage. Not sure how rain is linked with an increase in mileage!

One reason I can think of, is your AC usage. With rains, we have a colder climate that doesn't make your AC compressor run all the time even though you have AC on 100% of the time. This can contribute to an increase in mileage.

[silverado]

@figo_mba

3 reasons that i can think of

1) Cooler climate = Less stress on engine
2) Due to rains, driving style becomes smoother.
3) Less friction = Less Traction = Better mileage.

[clevermax]

Originally Posted by silverado

3) Less friction = Less Traction = Better mileage.

Can you please explain this point a bit more? I don't seem to get it..

[Viraat13]

My theory — Colder air = better combustion (which results in better FE).

[bluevolt]

Improved mileage is due to the fact that engine runs at cooler temperature than usual and the AC cuts off more frequently. Similar thread exists where we discussed how winters improve mileage http://www.team-bhp.com/forum/technical-stuff/94308-ah-winter-time-engines-feeling-better.html

I can not think of other reasons other than colder air, cooler engine, less compressor usage.