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Fuel efficiency theory


sisaacs918

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A gallon of gas weighs about 6 pounds (or so Google tells me), and I read somewhere on the internet that every 100 pounds on/in your vehicle affect your fuel efficient by 2-3%.

 

With that in mind, would continually driving around with only a few gallons in your tank compared to a full tank give you a positive increase in your mpg? What do you guys think?

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The high pressure fuel pump in modern vehicles with fuel injection gets cooled by the fuel in the tank.

Driving on a regular basis with a few gallons, will likely result in early failure of the fuel pump due to excess heat.

 

Having to refill at gas stations more often would reduce economy as well as the additional hassle.

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The fuel pump cooling myth is just a myth. The pump gets cooled by fuel going through it, not around it. On direct injection engines like the Ecoboost engines, the high pressure fuel pump isn't even in the fuel tank, it's directly mounted to the engine. No fuel around it and they survive just fine. It's only when you run dry and the pump starts pumping air, that's when it can overheat.

 

Absolutely driving around with less fuel will improve your mileage. In fact the North American Focus has a tank restriction that prevents you from filling up the tank to it's full capacity, just to reduce the weight so it could get a higher EPA fuel number.

 

But in the end the difference will be pretty minimal and the extra aggravation of stopping all the time wouldn't be worth it to most people, that's why I just fill it up full every time.

Edited by Waldo
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Weight plays only a small factor, gas savings is much more related to acceleration and speed.

 

Remember the Mobilegas Economy Run's of the 1960's? (Ok, I may be showing my age), but they would run different cars across country to test how good gas mileage cars (of that era) could get. To get the best milage they would train the drivers to accelerate by putting a raw egg between the accelerater pedal and their shoes. They had to drive without breaking the egg. Result was long, slow accelerations and best possible gas mileage. (They also used other tricks like having a good wax job and smaller drivers. And of course Mobil gasoline :-)

 

Sent from my Galaxy 5.

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I have a performance fuel pump that is mounted in the tank of my grand prix. The new pumps are not very big, and have to move a lot of gas. It only makes sense to me that a higher level of fuel would dissipate heat away from those small aerator style pumps. Heat is the enemy of electric motors and electronics.

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