I understand that colder temperatures have an effect on FE, but what is it that causes this?

Is it that on start up it takes longer to warm up?

Is it that it takes time for the batteries to come on line?

Is it that the ICE does not perform as well in the cold?

I noticed that my FE was steadily getting better as the weather started to warm up 53F up to 71F recently, and then...we had a cold snap...back down to 50F, and my FE took a dive, regardless of how careful I was.

So my question is...what's doing this?

 

Well, this is indeed a traditional issue with internal combustion engines.

The engine's optimal operating temperature needs to be a little higher because it facilitates a number of important things:
- It helps improve (lower) the viscosity of the oil. Colder oil means more resistance imposed on the engine.
- It helps the detonation of the fuel and air mixture. The colder the air the more fuel is typically added on the intake.
- It helps extend the life of the emission control systems as well as their effectiveness in reducing airborne particulate matter (their primary objective).

Now, these are just some of the main reasons - there are many more. The ECU/PGM-FI is specifically programmed to prioritize the warming up of the engine to meet these reasons. Its agressiveness depends on how much of a temp swing is required. Obviously, for those of us who live in cold countries this is an inevitable reality that we are used to.

However, a block heater can do wonders. Especially if you plug it to a timed power outlet for a couple of hours prior to using the car in the morning. I do this even during the summer months and it does help a lot. Maybe it is something that can work for you too?

Cheers;

MSantos

 

Thanks for that.


For the entire time I've had my HCH II it's been winter. Although the winter temperatures here are no where near as low as you get over there.
Typically no lower than 5C (41F) during the day and usually not quite freezing at night.

Nevertheless I assume that these low temperatures will have an effect on FE.

I'm hoping that 45MPG (US) that I'm averaging now will in crease over the summer.

Typically we get anything up to 100 - 105F max, but usually around 95F.

I always thought that once the engine was warmed up the colder weather was better because it meant the the cold air would expand more under combustion. On a foggy night this is really noticeable.

 

Combustion gives off heat.
It takes some time for the engine block to come up to its final temperature.
Hence low MPG during warm up.

Air flow constantly carries away some of the heat.
Some of the energy in the gas is always being used to replace the heat carried away.

If it is 20 degrees outside MORE energy in the gas is needed to replace the heat than is needed at 120 degrees.

Hence better MPG at warmer temps.

 

Kenny. So what are you doing to get 62.9...average!?

I mean...your not out there pushing it are you?

62.9 = 3.7L/100klm!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!


This is nuts!!

3.7...even if the motor wasn't running I'd be using more than that!

Now come on...what's your secret?

 

Cold temperatures have several negative effects on FE. In addition to what others have written:

• Cold air is denser than warm air, and therefore requires more energy to push it aside.
• Since more engine heat gets dissipated into cold air, keeping the engine at operating temperature is tougher.
• On hybrids, the auto-stop is less likely to engage. (On Civic hybrids, it won't engage at all if the windshield defroster/defogger is operating.) Last winter I was driving around one morning in 30F air (very cold for these parts). Even when the gauge showed the engine at or near regular operating temperature, auto-stop would not engage.

If there were a magical way to cool hot air without using any energy, summer would be the best time of year for FE. Since there isn't, and the A/C is a real gas hog, spring and fall are the best times.