How many miles left when gas meter says 0?

Why not run it dry and let us know ?

Keep in mind that the electric fuel pump in the fuel tank DEPENDS on the gasoline passing thru it for LUBRICATION. As the pump starts sucking air along with the gasoline, the pump's lubrications supply is also compromised. Keep doing what you're doing and somewhere down the road ... perhaps 70-100k miles, you'll have a repair bill for an expensive fuel pump. Completely avoidable.

most people wouldn't recommmend going much below a quarter tank anyway.

mrcheerful

Tom Ridge says we should always have at least a half tank. I agree.

One of the most common problems with habitually running your tank down to the point that you're literally "running on fumes" is that you suck up all the crud from the bottom of the tank into your filter and combustion system, potentially clogging or reducing the efficiency of either or both. Any mechanic will tell you this is an extremely bad practice and needs to be avoided.

Except when on long road trips we always keep the guage up to at least 1/2 tank or more. On road trips we'll start looking for a convenient station at the 1/4 tank point unless someone needs a restroom break before that point. Once we get below 1/8 tank we'll get gas from anyone, irregardles of brand.

Although both in our late 50s we are both "straight-through" drivers regardless of distance. In the wee hours of the morning those gas stations become few and far between. Driving after midnight we stop to top off (and stretch our legs & change drivers) at the 1/2 tank point. That's approx every 200 miles.

Hi Cliff,

Would you please explain your statement about sucking up crud from the bottom. I don't understand how having more gas in the tank will prevent the fuel pickup from getting the crud. Everyone seems to agree with you, including "any mechanic". I have seen this warning over and over about keeping your tank 1/4 full. I have never asked nor had explained to me why having more fuel in the tank prevents the pickup from sucking up the crud and water. I'm not trying to be antagonistic, I really don't understand how the amount of fuel in the tank affects the fuel pickup's propensity for ingesting crud and water.

Here is my understanding of the fuel pickup in the fuel tank. There is a pickup tube with a some sort of filter over the opening. The pickup is located near the bottom of the tank. It is not flush with the bottom of the tank, just near the bottom. It is firmly fastened there. It does not float at or near the top of the fuel. The pickup feeds the fuel pump which is usually located in the fuel tank too.

The CRUD in the tank is heavier than the gas, so it will form a layer on the bottom of the tank.

Water is certainly heavier than gasoline, so the water will accumulate at the bottom of the tank. (I'll leave it for another discussion about how the water gets in there, and how to get it out.)

If my understanding is correct, and I'm sure you (the Usenet community) will correct me if I'm wrong. The bottom of the tank should have the crud and the water.

When you have a little gasoline in the tank, it covers the crud and water at the bottom and then immerses the fuel pickup. Assuming you don't have too much crud and water in the tank, the fuel pickup will be in gasoline. At this point, the more gasoline you put in the tank the more head room you will have over the fuel pickup.

Now start driving down the street. The fuel and crud and water in the tank will be agitated, causing all three things to be mixed together into a suspension (not a solution). The fuel pickup will pull in the suspension, which includes mostly gasoline, but some suspended crud and water. The water should make it through the pickup screen, the pump and the inline fuel filter. Small (really small) percentages of water will not affect the fuel system or your engine. Really small crud will probably pass through without harm too. Larger crud should get stopped by the pickup screen and the inline fuel filter. Large amounts of crud will eventually plug the inline filter. I might guess the pickup screen might be somewhat self cleaning by the agitation of the fuel/crud/water solution.

So how does running the gasoline low in the tank affect the fuel pickup?

Ken - West Union, SC Population 270 + 2 (counting dogs and chickens) "If you only have a hammer, you tend to see every problem as a nail."

- Abraham H. Maslow

As I understand it the small amount of fuel sloshes about and agitates the junk more than a deeper amount of fuel will.

Imagine some junk in the bottom of a bucket full of water, give it a shake about and the junk on the bottom will hardly move, if you have a small amount of water in the bucket and shake it, then the junk will get mixed up into a solution quite easily.

mrcheerful

Yep. That makes sense. especially when you just give it a shake, but when you shake it for an hour, I'm going to bet that the junk in the full bucket gets stirred up too.

In your favor, even if the junk gets stirred up when the tank is full, it will be more dilute than when the tank is mostly empty.

I'm just not buying the empty tank / clog the fuel line argument. I do agree that a full tank will keep the fuel pump cooler and lubricated.

Ken - West Union, SC Population 270 + 2 (counting dogs and chickens) "If you only have a hammer, you tend to see every problem as a nail."

- Abraham H. Maslow

I could be wrong, but I think most cars these days have a float switch (or something equivalent) that shuts off the fuel pump when/if it's in danger. After all, you're about to coast to a stop anyhow, might as well save the pump.

Only time I ever had fuel contamination issues in any car was once when a filling station pumped in a load of water and garp. Car was sick almost immediately with a full tank.

-- Pete

RunnerBiker wrote:

The pump is shut off after the key is released from START to ON and the engine is not running after 2-3 seconds. Also many cars shut the fuel pump off when the air bags deploy or the car rolls on it's side or roof.

I was referring to fuel exhaustion.

-- Pete

Philip® wrote:

I know. The only fuel pump safeguards are the ones I listed and they are not for the pump's benefit..

Your safe for at least another 90 miles Douglas, just ignore the "Low Fuel" warning and keep driving. Always fill up when it's convenient to you, not when the car tells you.

Geez ... the dripping sarcasm and disdain by "wjfrancis" is remarkable. ;-)

Depends if you're uphill or downhill at the time.

John

WHEN THE CAR STOPPS RUNNING YOU HAVE NO MORE GAS. DO IT ON THE HIGHWAY IS MORE FUN!!

Douglas,

There are so many variations which make your question unanswerable.

1. Your level sender for the fuel tank may be slightly different to others.
2. Depends how light/heavy footed you are.
3. The terrain you're driving on, flat or uphill or downhill.
4. The speed you drive, each vehicle has a most economical cruising speed.
5. How many passengers and luggage you're carrying.
6. The speed and direction of the wind.
7. The condition of your engine and management system.

All the above factors can have an influence to a larger or smaller degree to your mileage. So always consider filling up when your tank reaches quarter full, or whenever you can if in the desert or wilderness.

Running out of fuel is inconvenient, time wasting, embarrassing and possibly dangerous should it occur in the wrong place. Remember you have then lost control of your vehicle and have to stop when the car says, not when you wish.

A vehicle without fuel is a chicane to other road users if you're unable to pull off the road.

Douglas,

By the way, you have a beautiful backyard.