100+ hypermiling / ecodriving tips & tactics

[redpoint5]

Originally Posted by 5inYSO

I have never agreed with topping off the tank. I'm surprised I don't see it mentioned more often. With a gallon of fuel weighing approximately 6 pounds and a 20 gallon tank, that's 120lbs. I usually fill no more than 1/2 tank, to save on hauling my fuel around.

Is this really a measurable fuel savings?

Like most everything, the answer is - it depends.

I don't see any penalty for hauling extra weight because I do a lot of coasting and highway driving. If you do a lot of stop and go driving, you will likely see a drop in mpg due to the extra weight. If you do a lot of highway miles, and especially P&G, you might actually see improved mileage from having extra weight.

For the typical driver, having less weight results in better economy. It's not worth the extra stops to the fuel station though.

[Mustang Dave]

Originally Posted by Frank Lee

That may be, but I'd like to see the fuel economy penalty for making 2x the pit stops.

Probably about 2%. Well within most people's tank-to-tank variability. And not doing a full fill-up every time is a rather imprecise way of calculating actual fuel economy.

[user removed]

When I get home on my bike, before I put it in the garage, I cool it off with an electric fan for about 10 minutes, so the fuel tank does not get heated by the engine.

regards
Mech

[Mustang Dave]

Good idea for a vehicle with the fuel tank vented to the atmosphere.

[euromodder]

Originally Posted by 5inYSO

I usually fill no more than 1/2 tank, to save on hauling my fuel around.

If you do a lot of city or stop and go driving, it could be noticeable and measurable.
On the highway, it doesn't make much difference.
In combined driving, it'll get lost in tank-2-tank fluctuations.

Is this really a measurable fuel savings?

Measuring it will be the hardest part.
It's got to help, as lower weight will always help.
It takes more energy to accelerate a heavier car, and its rolling resistance is higher.

Even in P&G situations, as you can't fully get back the energy that was put into the car.

Weight may seem to help the glide, but the energy had to go in first.
Same with gravity-extended coasting, you had to get the extra weight up the hill first.

People will do a lot of work to get rid of weight - like stripping the interior - carrying less gas is an easy way, though not everyone has 20 gallons to start with.

If you have a fuel station on a good point along your route, the extra stop won't make much of a difference.
If you have to drive around to get fuel, you might lose what you gained.

[euromodder]

Originally Posted by Old Mechanic

When I get home on my bike, before I put it in the garage, I cool it off with an electric fan for about 10 minutes, so the fuel tank does not get heated by the engine.

Would it help to stick some of that heat reflective under-the-hood foam/foil underneath the tank, to reflect the heat away from the tank ?

[PaleMelanesian]

I'm not posting those charts any more. The numbers are less conclusive now that I have more data. There is a slight gain toward empty, but it's less than 2% from F to E.

Just because it's too small to measure against the variables of daily driving doesn't mean there's no gain.

[ksa8907]

Would like to add, with a full tank the rear of the car would ride a little lower improving drag.

[redpoint5]

Originally Posted by PaleMelanesian

Just because it's too small to measure against the variables of daily driving doesn't mean there's no gain.

At some point, the "gain" is so small that it doesn't justify the lost time. Some might argue that it's just 5min of time wasted every week, but that adds up over years of driving (4hrs and 20min/year). Time is our most valuable resource because it is limited and can be traded for pursuits such as money or pleasure.

Even those that fill only to half a tank acknowledge the diminishing value of that practice, otherwise they would fill only to 1/4 tank, or 1/8 tank, or, you get the idea.

[PaleMelanesian]

You can see where I stand by reading my mileage log. My average fill for the last year is 11.3 gallons, in an 11.9 gallon tank.