Couple of tips on fue efficiency

[Dave - Dave.net.nz]

Also, based on his numbers, he should get about 20 mpg more without the air
conditioner, 6 mpg more when driving during the day without headlights and
5-10 mpg more by not using his radio. 60 mpg sounds about right.

just imagine if you started taking things like spare tires, radio, back
seats out, with the weight reduction you would get massive improvements

 

[Cam Penner]

That would be an interesting number to see.

How about the theoretical numbers-

DRLs are typically about 25w. Assume that
two of them require about 100w to run with dismal
50% efficiency of the alternator.

According to some quick research, a U.S. gallon of gas
contains about 44 Megajoules, and the gas engine is about
25% efficient.

So a car that gets 30 mpg at 60 mph is using 2 gallons
per hour, or 352 Megajoules per hour.

In that hour, the headlights have consumed 0.36 Megajoules.
(100 * 3600 seconds)

So the DRLs are using 0.1% of the engine's consumption.

Disconnecting the DRLs should see an improvement upwards
to 30.03 mpg from 30.00.

Those were closer to what I had worked on. It seems to me
that the power for DRL is not far off what many stereos are
run at. Add one psi to each tire, and you'll probably see
a bigger improvement. Or better yet, lose 10 pounds
yourself, and see a gas milage improvement.

 

[Don]

just imagine if you started taking things like spare tires, radio, back
seats out, with the weight reduction you would get massive improvements

It wouldn't take much to get to the point where you can drive 10 miles and
end up with more gas than when you started.

Don D.

 

[etienne]

If people wanted to save gas, they would stop driving SUV's, etc.....
DRL do not amount to that much fuel consumption.... 2-3mpg is
definitely not an accurate figure at all.

 

[Steve Bukosky]

The AC thing is a bit tricky as not all cars seem to respond
equally. My old Corsica 2.8LV6 uses only slightly
more gas when the AC is running, but the 2.2L Subaru
seems to use a lot. I also have a 1.5L Hyundai that gulps
gas like crazy with the AC on. I think that the bigger the
engine the less fuel is needed to run the AC (?). Why, how
I don't know. Maybe its just a perception as a big engine
uses more gas to begin with.

Perhaps because the percentage of load on the engine is less for a
large engine than with a smaller engine.

 

[Steve Bukosky]

CNN had a report on A/C vs. fuel economy not too long ago. The test results
(same car, same driving conditions, same weather and driver) revealed that
A/C usage hampered fuel economy at low speeds, and thus an open window would
be an economical alternative. On the other hand, they found that the A/C
system yielded BETTER mileage at highway speeds versus an open window due to
the aerodynamic effects of an open window. These results were A/C verses
windows, obviously using no A/C and the vent only will save gas over both,
since you retain the best aerodynamic efficiency and reduce the typical 5 hp
gas consumption required by the A/C system.

Mike

I can understand that. Was a changeover speed mentioned? In my mind
something around 45mph would seem right.

 

[Mike Lloyd]

as far as I recall they just referred to city and highway. do a Google
search on it. I'll do the same and let the NG know of anything relevant.

Mike

 

[Danny Russell]

Anything else, gang?

Coasting out of gear (idling engine) uses more fuel in any modern vehicle that shuts off the fuel
injectors during coast-down. -Danny

 

[Freedom55]

2 to 3 MPG (less pull on the alternator) in city driving
It ain't much but every bit helps!

I doubt it.

--
And it really doesn't matter if
I'm wrong I'm right
Where I belong I'm right
Where I belong.

Lennon & McCartney

 

[Dominic Richens]

Coasting out of gear (idling engine) uses more fuel in any modern
vehicle that shuts off the fuel injectors during coast-down. -Danny

eh?