Show #1149 a lady called and asked if her husband was crazy for only pumping a few gallons of fuel whenever needed. The man was convinced that the extra weight of a full tank would cause mpg to suffer. The guys said they agreed in principal, but I believe they missed asking a question about the model of car being discussed. I know it is not the case with all cars but some fuel pumps are lubricated by the fuel itself, and in the case of the Ford Explorer Sport I previously owned, constantly running with a nearly empty tank burned up the pump. Maybe it should be considered?
The pump burning up wouldn’t affect the mileage.
Stopping for gas means driving further (to and from the station) as well as stopping and starting the engine. Then there is the additional chance of getting water (rain, snow or condensation) in the fuel etc.
All considered, I believe he will get better mileage if he just fills it up like when it gets down to a quarter of a tank. Following my advice might give better mileage than he is now doing and save wear on the starter brakes etc.
I would guess following my advice might save more fuel than his method, maybe a 0.0023% improvement.I have to agree with JosephE on this one. In addition to just being a royal pain in the rear he is wasting gas just going to purchase more gas. I know people like this. They drive 10 miles across town to save a few cents on bread and milk. It does not compute.
If you use a gas station that is on your route, you don’t have to drive out of your way.
Isn’t that how most people buy their fuel anyway? Who drives out of their way to buy fuel? If I happen to be going to BJ’s anyway, I will fill-up the tank while I am there, but I don’t drive out of my way to get gas there. Doing so would cost more in burned fuel than I would save from the cheaper price.
Let’s see…
if your car is rated at 25 mpg city and 30 hwy, have a 15 gallon tank, drive mostly highway, and fill it every time it gets down to 1/3, than in 6000 miles you’ll stop 20 times to fill. And probably average 29mpg.
If you put in 3.3 gallons every time you stop, you’ll stop about 60 times in 6000 miles and probably average closer to your city rating, perhaps 26mpg.
All things considered, and since 10 gallons of gas weighs just over 60 pounds (2% of a 3000 lb car’s total weight) and doesn’t affect its aerodynamics at all, I don’t think the lady’s hubby’s theory is valid. Is he crazy? No way to know based on this information. If he is, what’s wrong with being crazy?
The insignificant amount of gas saved by only putting in enough gas for next trip or two…will be outweighed by the aggravation the first time you run out of gas in the middle of a snow storm.
I don’t think there will be any savings that can be measured. If you drive 20k miles a year…the savings might add up to $20. Not worth my time and effort to keep going to the gas station every other day to fill up.
I have a log book to keep track of my gas mileage. When I drive to work (mostly highway)…I average about 20mpg…When I travel someplace with family (all 5 in the truck)…I average about 20mpg.
Hmmm. Is he crazy? Who knows-obsessive for sure. Can’t believe people focus so much on MPG. So if it is weight, walk some more and take off a few pounds. Take out the back seat and anything in the trunk. Don’t allow passengers in the car unless absolutely necessary. What does a cup of coffee weigh? The goal is 60 pounds or better. Maybe he already did this which would put him in the crazed column.
Excellent points Bing.
I know I could stand to lose about…ohhhhhh…50 pounds, maybe 60. That might just be the best way I could improve my mileage!
In truth, 50 or 60 pounds woulnn’t make a measurable difference…but I like the idea.
I guess my point was lost. I was asking if they should have made the point that regardless of any mileage gains the detriment to the fuel pump would make this method of penny pinching unfavorable in the long run.
The possibility of damaging the fuel pump only occurs if you let the fuel get really low, like low enough to make a warning light come on. If there’s still a gallon or two in there when you buy fuel, the fuel pump should be fine.
Although it might bring scorn from others, I admit I do this, but not as bad as the caller’s husband. I’ve eliminated weight from my vehicle by removing the back seat that I never use (and gets in the way of disconnecting the fuel pump when I replace the fuel filter), and other various items that were cluttering my car. I don’t buy just a few gallons, but I fill my 11 gallon tank to the halfway mark most of the time. There’s always a gas station on my commute that I can stop at without going out of my way, and even though my fuel savings don’t amount to enough to actually measure, I don’t drive the car enough to make this practice a hardship or an inconvenience. My motorcycle fuel tank only holds 3.9 gallons, so stopping for fuel is something already do frequently. In fact, I find that fueling my motorcycle every day instead of every other day isn’t that much of an inconvenience. It saves me the trouble of using the fuel reserve switch, and it allows me to monitor my daily fuel use. The average cost of fuel for my commute is about $4.20 per day. 
I do fill the tank up all the way on my car sometimes, like when I take long trips, or when I am going to a wholesale club where gas is significantly cheaper than the gas stations in my neighborhood.
420 you say… hmmm.