Avoid Running on Empty

I got a piece of mail from my Credit Union with some tips on saving fuel.
One was to avoid running on empty. "When your car is on empty, you're
actually using more gas because your vehicle is running less efficiently.
Fill your gas tank when you have about a half tank." (Credit Union of NJ,
June 2007). I've never heard of this, so I checked the internet and found a
few mentions of this.

I don't get how having more fuel on board makes your car run more
efficiently.

 

Well I will tell you this, if it is a GM product it will cost you less
in long run to keep it above 1/4 or more because the pump in tank is
cooled and lubed by fuel and if you are one to run it on "E" a lot you
will shorten the life of your pump.

 

More fuel in the tank = more weight in the car. More weight to
accelerate and decelerate usually takes more energy. Perhaps this
phenomenon is caused by the curvature of the earth, in which case the
car will only get better gas mileage near the equator while driving west.

As for the fuel pump it seems the liquid flowing through it should
provide adequate cooling if it was designed correctly. If the fuel pump
was made by Ford then it was designed to be replaced, which in their
eyes was designed correctly.

Gyz

 

GM tank fuel pumps do suffer from a shorter life if you run them low a
lot.

 

I always thought that the "fuller fuel tank" rationale had to do with
evaporation. If there is more air space in the tank, there is more air
volume where the liquid can evaporate. Of course, the vapor can only
escape when you remove the fuel filler cap to gas up your car.

More evaporation = more gas used per unit of distance traveled = lower
"efficiency".

Just my 2 Yen worth.

73 de Jim

 

On the other hand, a full tank weighs more than an empty one. At six pounds
per gallon, the difference between a full tank and a nearly empty tank is
about 70 pounds in my Saturn SL2 -- and nearly two hundred pounds in my
Suburban.

Schlepping all that extra weight around cuts down on your fuel mileage.

 

Actually when the tank is nearly empty, the air that occupies the tank's
volume without the fuel has moisture in it and that moisture can condense on
the fuel tank's walls and then mix with the fuel. This is why I never let
my fuel get below half in the cooler winter months.

By the way, I personally agree with you and don't buy the rationale that a
fuller tank results in higher fuel efficiency either.

Bob