My theory of driving at night

[lyssword]

I suspect driving at night/evening will save up to 10% fuel economy.

pros

1. Colder air is more dense, more oxygen going into the engine = more efficient firing of cylinders
2. No need for air conditioner (which also saps xx hp's from engine)
3. Engine doesn't overheat as much.

cons

1. Lower visibility
2. Possibly more sleepy

 

[Excelsior]

Pros- less traffic

Cons- more drunks

 

[lyssword]

Originally posted by: Excelsior
Pros- less traffic

Cons- more drunks

That too, but I was thinking more in the context of interstate 100+ miles travel

 

[No1ustad]

I'm more awake at night anyways.

 

[dug777]

They can't use multanovas here at night, either

 

[darkswordsman17]

Actually, warmer air is better for fuel efficiency, colder air is better for power efficiency.

Not needing A/C is probably negated by the need to run lights (drains the battery, battery needs to be charged). I'm not sure which is more efficient (especially on a modern car).

Cooler air, like you say, is more dense, and thus there would be slightly more parisitic drag (aerodynamics). Also, more traffic is actually better for aerodynamics as you can draft more.

Lastly, take into consideration the differences in tire pressure (again very marginal, but the cooler air at night would lead to a drop in tire pressure which would affect rolling resistance).

Anyways, my point is, when considering all the factors, the difference should be pretty much negligible.

 

[TallBill]

Plus with less traffic you'll probably up your speed over whats prime for your car. Then again, with heavy traffic you'll go the opposite way.

I personally prefer driving at night just to avoid the traffic.

 

[OVerLoRDI]

I think on an interstate at night would be better. If you set cruise control at 70, no AC probably do better at 3am than say 3pm with you having to pass, merge, accelerate, brake, etc because of the other cars.

 

[markgm]

I usually prefer driving at night when I'll be entering a city, but for normal driving I would rather it be light out so I can see if there are any cops hiding anywhere. I get paranoid when I'm able to drive for long stretches at a time hitting anything close to the speed limit!

 

[smack Down]

If you want better gas millage tailgate a semi.

 

[faenix]

Originally posted by: smack Down
If you want better gas millage tailgate a semi.

qft mythbusters

 

[DrPizza]

Did you ever notice that the mileage ratings look like this:

36 hwy / 25 city

And not this:

36 hwy / 25 city / 40 night


Darkswordsman listed some of the same points I was going to make.

 

[FoBoT]

and when you need to drive and it isn't night? do you have a day->night machine?

 

[SoulAssassin]

Originally posted by: OVerLoRDI
I think on an interstate at night would be better. If you set cruise control at 70, no AC probably do better at 3am than say 3pm with you having to pass, merge, accelerate, brake, etc because of the other cars.

70? in what...a 45mph zone?

 

[feralkid]

Originally posted by: darkswordsman17
Actually, warmer air is better for fuel efficiency, colder air is better for power efficiency.

Not needing A/C is probably negated by the need to run lights (drains the battery, battery needs to be charged). I'm not sure which is more efficient (especially on a modern car).

q]





The alternator is always spinning, whether you use your lights or not. It has no effect on fuel efficiency.

The AC compressor only spins when you have the AC turned on.

 

[Josh123]

I wanna go fast














at night.

 

[nweaver]

driving at night means the kids are asleep. Everyone knows the whining/fighting reduces fuel mileage. Not to mention less pit stops.

 

[Kirby]

It's so hot here you still have to run the AC at night.

 

[ElFenix]

Originally posted by: faenix

Originally posted by: smack Down
If you want better gas millage tailgate a semi.

qft mythbusters

big time. and you know what's on the interstate at night? semis.


then again, getting killed because you're 3 feet off the semi's bumper isn't good for mileage either.

 

[darkswordsman17]

Originally posted by: feralkid

Originally posted by: darkswordsman17
Actually, warmer air is better for fuel efficiency, colder air is better for power efficiency.

Not needing A/C is probably negated by the need to run lights (drains the battery, battery needs to be charged). I'm not sure which is more efficient (especially on a modern car).

q]

The alternator is always spinning, whether you use your lights or not. It has no effect on fuel efficiency.

The AC compressor only spins when you have the AC turned on.

Yes, but running more electrical stuff requires a higher draw, and thus more pull from the engine.

 

[SynthDude2001]

Originally posted by: nkgreen
It's so hot here you still have to run the AC at night.

I was about to say the same thing. Clearly the OP doesn't live in an area where it's still warm and/or extremely humid in the middle of the night

 

[feralkid]

Originally posted by: darkswordsman17

Originally posted by: feralkid

Originally posted by: darkswordsman17
Actually, warmer air is better for fuel efficiency, colder air is better for power efficiency.

Not needing A/C is probably negated by the need to run lights (drains the battery, battery needs to be charged). I'm not sure which is more efficient (especially on a modern car).

q]

The alternator is always spinning, whether you use your lights or not. It has no effect on fuel efficiency.

The AC compressor only spins when you have the AC turned on.

Yes, but running more electrical stuff requires a higher draw, and thus more pull from the engine.

No.

The alternator does not "gear down" or demand any more effort from the engine, no matter what electrical accessories are being used.

 

[ahurtt]

Originally posted by: feralkid

Originally posted by: darkswordsman17

Originally posted by: feralkid

Originally posted by: darkswordsman17
Actually, warmer air is better for fuel efficiency, colder air is better for power efficiency.

Not needing A/C is probably negated by the need to run lights (drains the battery, battery needs to be charged). I'm not sure which is more efficient (especially on a modern car).

q]

The alternator is always spinning, whether you use your lights or not. It has no effect on fuel efficiency.

The AC compressor only spins when you have the AC turned on.

Yes, but running more electrical stuff requires a higher draw, and thus more pull from the engine.

No.

The alternator does not "gear down" or demand any more effort from the engine, no matter what electrical accessories are being used.

QFT.

Only running the AC compressor requires more work from the engine. Once the car is running the electrical system is powered by the alternator which is always cranking as long as the car is running. Any excess power cranked out by the alternator that is not consumed by the cars electrical system can be diverted to charge the battery. But turning on your headlight or radio or operating your power windows, etc. . .does not increase demand on your engine and causes no extra fuel consumption.

 

[rh71]

"don't fill up your gas tank during the day due to evaporation"

I read that once.. how true is this ? Isn't the tank going to start to evaporate the next day in the sun anyway ? How much could you possiblly penny pinch ?