Real time "Miles Remaining"

[santov]

Thought this was funny:

Whenever I'm below half a tank I plan my fillup. I guess I'm paranoid about needing to go somewhere in a hurry or emergency basis and then have to stop for gas. When I get to 1/4 tank I switch the computer to miles remaining.

I pulled into the gas station to fill up. Had the top down and The Black Keys playing. So I thought I'd leave the ignition on (ACC) and pump gas. Whenever I fillup I log my stats into ACar (fuel tracker for Droid). First thing it needs is the odometer reading so I walk around the car to get the odo and the miles remaining is going up like crazy! It was entertaining to watch how fast the values are being computed.

How accurate is this thing? Next time I gas up I'll note how many miles left are being reported and try to estimate the margin of error.

My MPGs have been on a down trend lately. Not sure why... I don't think I've been driving faster/aggresively lately.

-V

[mfanatic325]

They're only estimates for the most part. Not extremely accurate. I've had an acquaintance claim that they've run the meter down past "0 miles left until fill up"
I asked what happened thereafter. They said past "0", it becomes dashed lines "---" and at that point you've still got about 1/4 mile at city speeds

[bhoch]

I usually get gas at the 1/4 tank mark. This is only because I did not do that one time on my daily commute and I got stuck in traffic for about 1.5 hours (could not exit highway either) and I watched as the silly little light came on, then the miles till empty became single digits, etc.. When I was finally able to pull into a gas station, it said 3 miles to go. Since then, I just get gas whenever it gets close to 1/4 tank and don't worry about it.

[zMpower08]

I have been at --- before for at least 10 minutes of extra driving frantically trying to find a gas station that was actually open.

[007MCoupe]

IT's an estimate for how many miles you could go at your 'current' speed. If you're doing a lot of stop and go, the miles-to-go will decrease quicker than highway, or catching green lights.

[ZZZZ]

Yes with all BMW's with miles remaining computers---if you keep your ignition on, and the computer on "range remaining" then top up your gas you'll see the numbers counting up quickly as the computer adjusts with the fuel level sensors.

BMW Gas Tanks traditionally have a hump in the middle where the exhaust pipes and drive shaft go. (Think of an upside down letter U). So gas can get trapped on the left and right sides of the tank, and the left/right sides may have different levels of fuel. So we actually have two level sensors. Drivers side and passenger side. The computer averages the amount of fuel reports by both fuel level sensors and the computer reports the average. On a side note, this means that if you fill up 100% and the dash reports only 1/2 tank, then one of your sensors is kaput.

The range remaining is very accurate, providing your upcoming driving terrain + style is the as it has been for the past.

The calculation is simple. What is your average MPG (or L/100km) x Fuel Remaining in Tank = Range.

So if your range is selling you 100 miles left but you've been cruising on the highway, but then you fall into some hilly city streets, you can expect your actual range to be much less. Likewise if you've been driving hard and revving the engine, then you cruise, then obviously your range will increase too. The good thing about the system is it's always calculating your average MPG on the fly and adjusting your range in real time.

I know on the e46 it calculates based on the last 50 miles you have driven. I assume the same is on the Z4.

[Pheonix]

DO NOT trust the indicator! I learned this the hard way last summer and got stranded in the middle of no where New Hampshire last summer. The Service Manager told me to take that number divide by 2 and substract 10 miles (still might still be in trouble). As mentioned above, our gas tank has a hump in the middle and the gas might got slushed to the wrong side of the tank! Plus, it also depends on your driving habit and terrains as well. As we all know, one could get as low as 11 MPG or as high as 23MPG (for the ///M)!

[Nikki]

You can go pretty far on ---. I think you have about a gallon left at that point. I've hit it a few times but the worst was actually last week I drove with it on --- for about 20 minutes through traffic in Beverly Hills on my way to La Brea, and couldn't find a gas station in sight. OF COURSE when i finally did find one it was 50 cents higher than what I pay out in Malibu.

[ZStig]

I think once you get down to about 8 or so miles left, it goes to _ _ _

[r4gs]

i've gotten close to single digit miles remaining but always fill up with about 12.5 to 13 gallons, meaning there's between 1 to 1.5 gallons at least in reserve (14.5 gallon tank) that should equate to between 10 and 20 miles give or take. what's more pressing is that the manual recommends against running on low fuel to avoid fuel starvation. the same applies in the aviation world where having 400 pounds of fuel remaining aboard a t-38 (4006 pounds full tank) equates to emergency fuel and a very real and immediately possibility of either or both engines flaming out from fuel starvation.

[esqu1re]

It's also important to have fuel in the tank in case of emergencies, so you can get out of town without having to rush the gas station first. The last zombie attack should have taught us that.

[dazed^]

Isn't there also the issue of getting debris in the engine if you completely empty the tank? That's assuming that most contaminants sink to the bottom of the tank and normally remain there.

[beta]

The manual specifically mentions that you should not let it get below... I think it was 40 miles estimated. I'll get the right number when I get home unless someone else chimes in.

[ZZZZ]

Originally Posted by dazed^

Isn't there also the issue of getting debris in the engine if you completely empty the tank? That's assuming that most contaminants sink to the bottom of the tank and normally remain there.

1) The intake for the fuel sender is at the bottom of the tank anyway. So debris that drops to the bottom of the tank would be sucked up. Stuff that floats at the top of the tank, or any oils/water that floats at the top of the gasoline in a layer however, will be sucked up when the tank runs low.

2) That's what the fuel filter is for. Picking up the debris that ends up in the fuel.

[Nikki]

Originally Posted by Roffle Waffle

I think once you get down to about 8 or so miles left, it goes to _ _ _

nah it goes down to 3, 2, 1 then ---

[mfanatic325]

Yeah I always fill up not shortly after the fuel light comes on (typically ~40-50 miles left on the counter, irregardless of how I'm driving)--if not sooner. This way I can survive any zombie attacks or the end of the world and have a Z4M getaway

[pokeybritches]

If anyone ever carjacks me, they won't get more than 10 miles away before they run out of gas. No high speed chases for either of my Z's.

[gcochard]

Originally Posted by ZZZZ

1) The intake for the fuel sender is at the bottom of the tank anyway. So debris that drops to the bottom of the tank would be sucked up. Stuff that floats at the top of the tank, or any oils/water that floats at the top of the gasoline in a layer however, will be sucked up when the tank runs low.

Water sinks to the bottom of gas tanks. Planes have drains at the low point so you can pull all the water out before startup. If you have to switch tanks in mid flight, and the tank has water in it, you'll get a flameout there too.

Since cars have only one tank, it'll be pulled through when you're cranking or shortly thereafter.

[Finnegan]

Originally Posted by pokeybritches

If anyone ever carjacks me, they won't get more than 10 miles away before they run out of gas. No high speed chases for either of my Z's.

Well, that's an advantage in that situation! Of course, when the zombies attack you'll be SOL though!

Better hope Mfanatic is close by with an open passenger seat in that situation! He's prepared for those pesky zombies....

[Jbs]

I usually put 20-40 in at a time when it gets down to 30 miles or so. thats with a 60 mile commute, so its pretty often