Dreaded "30 Mile" Gas Range...

[J312]

Pumps have filters, don't worry about sucking anything up.

Pumps create heat, as the fluid is pumped through the pump, it cools it. It does not need to be submerged, it just needs to be pumping fluid through it. (for example, if you keep using your washer fluid pump without any washer fluid, it will heat up, seize, burn a fuse, or ruin its windings)

As far as the warning in the BMW book, its providing info for two reasons. You only have ~30 miles left when the light comes on. And legally, Don't be going 80-MPH when your car dies out and you start losing all those fun safety features.

[turner23]

Originally Posted by J312

Pumps have filters, don't worry about sucking anything up.

Pumps create heat, as the fluid is pumped through the pump, it cools it. It does not need to be submerged, it just needs to be pumping fluid through it. (for example, if you keep using your washer fluid pump without any washer fluid, it will heat up, seize, burn a fuse, or ruin its windings)

As far as the warning in the BMW book, its providing info for two reasons. You only have ~30 miles left when the light comes on. And legally, Don't be going 80-MPH when your car dies out and you start losing all those fun safety features.

I never let my tank get below half way, because I don't want to be waiting in 5 hour lines at gas stations again the next time there is a natural disaster or terror attacks. That is just one of the things I promised myself while waiting for gas in NY after the last attacks.

True, a fuel pump contains a filter, but the point is if you run out of gas, you'll likely burn the pump up.

"And legally, Don't be going 80-MPH when your car dies out and you start losing all those fun safety features." What legality is there about going 80mph? if you run out of gas going 45, the consequences are the same; speed is irrelevant.

I would hate to find myself with your level of anxiety/paranoia. Sorry you had to wait 5 hours for gas, but to fill up at 1/2 tank...that's excessive, IMO.

[AlienDNA]

Originally Posted by turner23

"And legally, Don't be going 80-MPH when your car dies out and you start losing all those fun safety features." What legality is there about going 80mph? if you run out of gas going 45, the consequences are the same; speed is irrelevant.

I think J312 just means that BMW is trying to avoid liability if someone's car suddenly runs out of gas and dies at highway speed and they creamed from behind by a bus, or they lose the security of DSC if they happen to be relying on it at the moment or something. I think J312 was just exaggerating for colourful effect. The potential for trouble outside the car if the engine dies is greater at 80 than at 45.

[Axiom]

Originally Posted by Lester

This topic comes up time and time again. Can someone from the 'run it on empty' camp please explain what good this does? How does it help? What are the benefits?

Regardless of what you think about anecdotal evidence about burning up fuel pumps prematurely, or causing potential lean spots in your fuel, letting sedimets pass into the engine, or creating potential for condensation (water) in your fuel. Ignoring all of that - please sell me on the benefits of running the tank on the empty third most of the time. As opposed to running on the top half.

We are waiting.

Ive seen some racecars run a tank down until they start to lose fuel pressure. But then they switch to a reserve tank, do one more lap, then pit. However these cars are not boosted like ours and nobody DDing their car is trying to get that extra lap in or shave off those few tenths of a second from having a lighter car with no fuel in it.

There really is no reason to run your tank down that low and yes, you can cause engine damage from running your tank so low. I just recently had a friend who threw a rod in his unmodded Mazdaspeed Protege from a bad misfire. This was not related to not having enough fuel in the tank, but if you starve our motors of fuel, you could get a misfire, and if its bad enough-- you could end up with a hurt motor or worse..

edit: im pretty sure you will damage the motor from running it low on fuel before you damage the fuel pump. Thats my opinion.. Its not like your car will explode either if you run the tank below 30 miles just take it easy on the car until you can get to a fuel station.

[tbird]

Most posts I see here focus on "sucking up sediment" and "harming the fuel pump". Both carry weight. Obviously, the fuel filter will hold back sediment, but what if it has reached its max? Fuel pump, how much harm? Well, the question should be "Do you want to reach that point?", that sounds better to me.

But I think that besides the technical side to the question here should be the common sense points, and IMHO these matter a bit more.

1) Do you want to actually run out of gas?
2) Do you want to be stuck somewhere, and then deal with the towing and the waiting and all of that?
3) Don't know if it is a standard charge across dealerships, but down here in S.FL, they charge $500 to get your car back to normal if it runs out of gas.

Whether the fuel pump burns up or not, whether the fuel filter works or not, I simply don't want to lose my time, patience, and money. Again, just my two cents of humble opinion, take it for what it's worth.

[Axiom]

Ha same thread in the 135i section... this is what I posted:

Ive seen some racecars run a tank down until they start to lose fuel pressure. But then they switch to a reserve tank, do one more lap, then pit. However these cars are not boosted like ours and nobody DDing their car is trying to get that extra lap in or shave off those few tenths of a second from having a lighter car with no fuel in it.

There really is no reason to run your tank down that low and yes, you can cause engine damage from running your tank so low. I just recently had a friend who threw a rod in his unmodded Mazdaspeed Protege from a bad misfire. This was not related to not having enough fuel in the tank, but if you starve our motors of fuel, you could get a misfire, and if its bad enough-- you could end up with a hurt motor or worse..

edit: im pretty sure you will damage the motor from running it low on fuel before you damage the fuel pump. Thats my opinion.. Its not like your car will explode either if you run the tank below 30 miles just take it easy on the car until you can get to a fuel station.

[Lester]

This topic comes up time and time again. Can someone from the 'run it on empty' camp please explain what good this does? How does it help? What are the benefits?

Regardless of what you think about anecdotal evidence about burning up fuel pumps prematurely, or causing potential lean spots in your fuel, letting sediments pass into the engine, or creating potential for condensation (water) in your fuel. Ignoring all of that - please sell me on the benefits of running the tank on the empty third most of the time. As opposed to running on the top half.

I can't think of a single reason for running on the bottom third on a regular basis. I know lots of people do it. I blame it on tardiness and procrastination. Some people just don't want to part with the extra $30. A whole year's interest on $30 these days is about 75 cents.

No matter what car I have ever owned, BMW or Chevrolet, Fiat or Dodge - I always run on the top half - long trips excluded. Racing is not normal, so do what you want there. I guess I just don't understand why some people run from day to day adding $10 worth of fuel every time the warning light goes on. It seems like a silly way to do business. But that's what living in a free country is all about.

[JBurer]

Xyloft is correct. The issue is running the motor lean on a low tank - not engine wear from stop and go traffic.

Fuel filters remove any debris from the tank. Man... some of the stuff I read on here!!

Original poster - unless you are driving significant distances out of your normal commute, filling your tank up when it is 1/8, 1/4 or 1/2 empty has no correlation to what it's costing you in fuel costs to drive each mile.

Originally Posted by Xyloft

I think they are trying to prevent damage from running out of fuel and causing damage.

think abou thow lean the motor for would be for a few RPM's if you were WOT, and you ran out of fuel. I mean I woulnt *think* the injectors are going to be 100% then 0% instantly. i would think you'd get and airfuel mix in the fuel lines and you'd run dangeriously lean (especially for you 135 folks).

I'm with a few other posters...fill up at a 1/4 especially if you're traveling places where you know you can't get gas.

[jeremyc74]

Originally Posted by Lester

This topic comes up time and time again. Can someone from the 'run it on empty' camp please explain what good this does? How does it help? What are the benefits?

Regardless of what you think about anecdotal evidence about burning up fuel pumps prematurely, or causing potential lean spots in your fuel, letting sediments pass into the engine, or creating potential for condensation (water) in your fuel. Ignoring all of that - please sell me on the benefits of running the tank on the empty third most of the time. As opposed to running on the top half.

I can't think of a single reason for running on the bottom third on a regular basis. I know lots of people do it. I blame it on tardiness and procrastination. Some people just don't want to part with the extra $30. A whole year's interest on $30 these days is about 75 cents.

No matter what car I have ever owned, BMW or Chevrolet, Fiat or Dodge - I always run on the top half - long trips excluded. Racing is not normal, so do what you want there. I guess I just don't understand why some people run from day to day adding $10 worth of fuel every time the warning light goes on. It seems like a silly way to do business. But that's what living in a free country is all about.

This question was answered for you in the other thread where you asked. There is no "run on empty" camp. There is a "don't go below 1/4 tank or you will damage your car" camp, and a camp that says you can drive it as far as you're comfortable with before you fill up and nothing bad will happen.

No one is trying to sell you on the idea of only filling up the lower half of the tank, only that you're not going to hurt the car by using the last 1/4.

[jeremyc74]

Originally Posted by tbird

Most posts I see here focus on "sucking up sediment" and "harming the fuel pump". Both carry weight. Obviously, the fuel filter will hold back sediment, but what if it has reached its max? Fuel pump, how much harm? Well, the question should be "Do you want to reach that point?", that sounds better to me.

The sediment argument has no weight at all. The pump alway pulls from the bottom of the tank no matter what the fuel level is. If there's stuff floating on the fuel you might pick that up when you get very low, but honestly if it's light enough to float it's not going to be an issue.

[968PORSCHE]

Ok, looks like someone already pointed out that the pump is cooled by the gas, and that the filter actually does it's job. So not there is not a bunch of crap at the bottom of the tank like a 65 Mustang. I just pulled the plug out of the bottom of my Porsche tank and lo and behold, after 15 years and 160K miles, no crap at all. Just gas. And yes there was a screen to catch stuff.

So if you're really low on fuel just don't drive so crazy that the pump starves for fuel because you are trying to make three .98 G turns in a row. It's probably pretty hard to get the pump to starve, just be reasonable with it.

[Lester]

That reminds me - I'm just above 1/2 full - time to top it up tomorrow. Gas is cheaper on Tuesdays in Vancouver.....

[TT1351]

I think it's definitely a cooling issue, and BMW goes to great lengths to cover their asses with regards liability issues. So if they suspect there is a potential for failure they stop at nothing to prevent a failure that might be a remote occurrence. From what I have read the fuel pump even on a good day is somewhat of a potential weak link. FWIW I have run mine to zero miles and then some with no issue, but at the end of the day an ounce of prevention is worth not having to deal with fuel pump issues. Just my thoughts.
Fran

[Lester]

Life is good. Super 94 Octane at Petro Canada for C$1.039 / litre. Filled up (23.4 l) from 5/8 full for just $23.14. Now I can sleep well tonight, don't have to worry about frying MY fuel pump.....

[J312]

Originally Posted by AlienDNA

I think J312 just means that BMW is trying to avoid liability if someone's car suddenly runs out of gas and dies at highway speed and they creamed from behind by a bus, or they lose the security of DSC if they happen to be relying on it at the moment or something. I think J312 was just exaggerating for colourful effect. The potential for trouble outside the car if the engine dies is greater at 80 than at 45.

Exactly. Thanks.