I live in Denmark and drive a manual gear-shift car (like most people
here). Fuel/gas is very expensive here, so I'm looking for ways to
save money when driving. I drive a 1999 Nissan HB, 1.4 liter 16V
engine with fuel injection. It's supposed to go 14.4 km/liter. So far,
the best I've done is 13.2, but I drive a lot in the city.

My question is this: When I can see far ahead that I can keep going
without my foot on the speeder, is it better to shift to neutral/hold
down the cludge than it is to just let go of the speeder (driving the
highest gear possible)? Since it's an injection engine, shouldn't it
cut the gas supply to the engine entirely when no extra gas is needed?

Also, I've been measuring the milage, and I can't see a great
improvement when trying to drive "economically". Do these efforts
matter in general, or are there better ways to achieve better milage?

There are a number of steps you can take to make sure that you are
getting the best possible fuel economy.  Many of them are listed in
the following article, "Fuel-Saving Tips" by Ann Job, MSN Autos
http://autos.msn.com/advice/article.aspx?contentid=4018909&src=News:

Have your vehicle serviced regularly to ensure that your air filter
and fuel filter are clean and that your spark plugs are not dirty.

Keep your tires inflated and your wheels aligned.

Do not carry any unnecessary items in your vehicle.  The extra weight
adversely affects gas mileage.

Drive smoothly without sudden accelerations and stops if you can do so
safely.  In the case of your car, with a manual transmission, coasting
is most efficiently done with the car in neutral or with the clutch
in.  Most automatic transmissions disengage the torque converter when
the gas pedal is not pressed to enhance coasting.  With a manual
transmission, you have to do this yourself to prevent the engine from
slowing the vehicle and to minimize the engine's RPM's.  However, this
could be quite dangerous if you need to accelerate suddenly to avoid a
collision.  Even while coasting with an engine with fuel injection,
gas is still provided to the engine to keep it running.  However, it
is done so at the idling rate.  You would need to obtain a hybrid
vehicle to have the capability of having the gasoline engine shut off
when it is not needed.

Drive more slowly.  Most vehicles get optimum gas mileage at 55 mph
(88.5 kph).  Higher speeds result in worse fuel economy.

Avoid idling and heavy traffic.  You get 0 kilometers per gallon when
you are not going anywhere.

According to the article, driving smoothly, not exceeding 55 mph (88.5
kph), and keeping your tires inflated are the three most effective
techniques you can use to boost your gas mileage if your automobile is
otherwise functioning well.  As gasoline has grown a lot more
expensive here in the United States recently, I can readily identify
with your concern.  I hope these ideas assist you in reducing your
gasoline consumption.

Sincerely,

Wonko

Thanks a lot!  Everyone should read this.

Good job!

Hi bokajsen-ga,

  In addition to the valuable tips provided by  wonko-ga, you
might find the following facts useful:

i) All the internal combustion engines have a specific rpm at which
they achieve maximum efficiency(may not have max torque at this rpm).
If you make sure you are driving at this particular rpm most of the
time you could benefit by the same.  If you do not have a tachometer,
I would advise you to have one installed.

ii) Doing quick gear shifts at the right rpm is also supposed to save
you on gas mileage.  You could benefit from a oil pressure gauge to help
with precise gear changes.

iii) Make sure you are using the right octane rating gas for your car.
If you tend to use lesser octane rating gas, this could lead to knocking
and automatic detuning, which will reduce your overall compression efficiency.
Also what you see is not what you get, so try maintaining logs with a
particular gas station to figure out the quality of the fuel.

iv) Since you have a fuel injection engine, you could increase efficiency
of the engine by installing a turbo charger. This assumes that the cost
savings achieved is more than the installation of the turbo charger and
the increase in price for the high octane gas.  This approach might not
work, if your car is already utilizing a very high compression ratio.

v) You might be able to get back more gas mileage on a high mileage car,
just by replacing the piston rings(do not attempt to do this yourself,
since it could cause permanent damage to engine walls defeating the benefit).

vi) You could also benefit if you live in a colder climate, by using a
jacket/dipstick heater, that could help the engine attain higher operating
temperature(and thus efficiency) also reducing the wear on the engine.

vii) You could try a less viscous engine oil that could help reduce the
frictional losses during engine lubrication.  This may not be the right
solution, if lot of city driving(and engine heating) is involved, or if
you live in a hotter weather.

Hope you find these tips useful.

Regards
ldavinci-ga