[flash3]

All,

I am at half tank now since picking up the X3 and trying to figure out when will be the best time to fill the tank usually on my x3. Is it best to fill the car @ half tank, quarter of a tank etc? Is there a best time/level?

[Mako]

Before it's empty is the best time.

[Nahoa]

Originally Posted by Mako

Before it's empty is the best time.

It'd taken so much restraint not to write that, and then you did . . .

[Lotus7]

Anytime it's convenient, as long as you don't risk running out of fuel. Modern, high-tech engines, especially the N55, can be damaged by being allowed to run down to an empty tank. Allowing air to enter fuel system can result in damage to the LPFP (low pressure fuel pump) the infamous HPFP (high pressure fuel pump), the engine's exhaust valves, and the exhaust O2 sensors because of the excess O2 present as the engine runs dry.

I never like to see the gauge get below 1/8 tank. I haven't seen the "low fuel warning" yet, but I suspect it will trigger at between 1 and 2 gallons remaining.

[flash3]

Originally Posted by Mako

Before it's empty is the best time.

I knew that was coming. lol

[Nahoa]

Ok, I try never to go below 1/2 tank for safety. May sou d paranoid, bu it's mattered more than once before.

Folks used to talk about it being a good idea to regularly take it down close to zero to consume sediments at the bottom of the take to keep the from building up over time. Any truth to that? Applicable to our current vehicles and fuel?

[flash3]

Originally Posted by Lotus7

Anytime it's convenient, as long as you don't risk running out of fuel. Modern, high-tech engines, especially the N55, can be damaged by being allowed to run down to an empty tank. Allowing air to enter fuel system can result in damage to the LPFP (low pressure fuel pump) the infamous HPFP (high pressure fuel pump), the engine's exhaust valves, and the exhaust O2 sensors because of the excess O2 present as the engine runs dry.

I never like to see the gauge get below 1/8 tank. I haven't seen the "low fuel warning" yet, but I suspect it will trigger at between 1 and 2 gallons remaining.

Thanks again, as always, for the info

[Lotus7]

Yep: If you run a X3 dry, you might as well just leave it parked by the side of the road with a "FOR SALE - BEST OFFER" sign attached. The engine, transmission, transfer case, all four axles, exhaust system, brakes and the hood ornament will all be toast. It's almost as bad as getting spray car wash soap on your aluminum intercooler.

[Lotus7]

Always take any free internet information with a grain of salt, or better yet a few hundred milligrams.

[Nahoa]

How many mg per grain, again?

[Lotus7]

Originally Posted by Nahoa

How many mg per grain, again?

1 grain=64.79891milligrams."

[Nahoa]

Originally Posted by Lotus7

1 grain=64.79891milligrams."

Adding a 64.79891 mg salt spoon to my keychain so I can readily take a grain, as needed . . .

[Ultimate Driver]

Originally Posted by flash3

I knew that was coming. lol

For what it's worth, I would disagree with that comment ("best to fill it before the gas runs out") - even when you almost run out of gas, the X3 keeps going - at least for the older X3s.

I ran the old E83 down to less than "20 miles remaining", well past the low fuel warning sign, several times. Once in particular I actually reached "2 miles remaining" (for the critics, I was on the State thruway, with no exits, and the state troopers closed off the only service center on that stretch)!

While I do not recommend anyone try this, I can say that at all of these times, there was no deterioration of performance or any ill-effects to the X3. I have no way to confirm the F25 will behave similarly (and I hopefully will never have to find out).

[Lotus7]

Originally Posted by Ultimate Driver

For what it's worth, I would disagree with that comment ("best to fill it before the gas runs out") - even when you almost run out of gas, the X3 keeps going - at least for the older X3s.

I ran the old E83 down to less than "20 miles remaining", well past the low fuel warning sign, several times. Once in particular I actually reached "2 miles remaining" (for the critics, I was on the State thruway, with no exits, and the state troopers closed off the only service center on that stretch)!

While I do not recommend anyone try this, I can say that at all of these times, there was no deterioration of performance or any ill-effects to the X3. I have no way to confirm the F25 will behave similarly (and I hopefully will never have to find out).

Presumably, BMW has been conservative in setting the point the warnings start. If you actually reach the point where the pick up tube becomes uncovered and starts "sucking" air it will be very apparent because of the misfiring that will occur. The engine may still run, but it will run badly. At that point, it's probably a good idea to shut it down immediately, rather than try to limp a few miles more.

The LPFP is cooled by fuel and the HPFP is lubricated by fuel. The O2 sensors can be damaged by one severe overheat cycle, which can easily happen if the mixture becomes very lean as you run out of fuel. Although it's counter intuitive, less fuel actually means a much hotter combustion process (too much oxygen).

[Beyu]

So is it bad to wait and fill up the car when the gas light (30-50 miles left) turns on? Its not like there aren't any gas stations close to my house but I rather fill up my car once a week vs twice or more.

[sfax]

Originally Posted by Ultimate Driver

For what it's worth, I would disagree with that comment ("best to fill it before the gas runs out") - even when you almost run out of gas, the X3 keeps going - at least for the older X3s.

I ran the old E83 down to less than "20 miles remaining", well past the low fuel warning sign, several times. Once in particular I actually reached "2 miles remaining" (for the critics, I was on the State thruway, with no exits, and the state troopers closed off the only service center on that stretch)!

While I do not recommend anyone try this, I can say that at all of these times, there was no deterioration of performance or any ill-effects to the X3. I have no way to confirm the F25 will behave similarly (and I hopefully will never have to find out).

This doesn't help much ....

You can see "exactly" how much is in each part of the tank to 1/10L by going into the "secret" menu on the dash. The one where you have to enter part of your VIN

[xDrive35i]

Originally Posted by Nahoa

It'd taken so much restraint not to write that, and then you did . . .

[Bimar]

i fuel when i see the cheapest price

[sfax]

Originally Posted by sfax

This doesn't help much ....

You can see "exactly" how much is in each part of the tank to 1/10L by going into the "secret" menu on the dash. The one where you have to enter part of your VIN

This is what I mean BTW....

Originally Posted by perto

Have anyone find the hidden menu in the idrive? You have to push the start button and the trip reset button simultaneously for a couple seconds(not pushing brake pedal)then ad the sum of the five last digits in the vin (like 5 if if you have 11111) and enter the sum in the right sub-menu. This should work for F10, curious if it works for F25.

[rs6655]

Originally Posted by flash3

All,

I am at half tank now since picking up the X3 and trying to figure out when will be the best time to fill the tank usually on my x3. Is it best to fill the car @ half tank, quarter of a tank etc? Is there a best time/level?

The short answer is never let it get low enough to run out. Not just because you'll have to walk but because it damages your fuel pump.

I know it sounds counterintuitive but the fuel actually runs through the motor of electric fuel pumps. As such they are cooled and lubricated by the fuel. If you run dry your pump is running with no lube and coolant. I try to keep my tank above 1/4.