Z3M Fuel Capacity & Gauge Accuracy

[SNR727]

Quick question for ya'll.

I understand the Z3M to have a 13 gallon tank with a 2 gallon reserve. (give or take a little)

I find on the gauge from 1/2 to empty goes real fast. But from full to half goes pretty regular.

Today I rolled in to get some gas just as I got to the half tank mark on my gauge. It took 10.37 gallons - ($44 in these parts)

Two part question:

Is it 13 + 2 (15) or 13 including 2 for reserve?

Do you all have a similar experience with your gauges? (Assuming you have the gauge that actually goes to full - this is my first Z3 that actually goes to full. The others only ever went to 3/4)

Out of habit I always tend to fill up at or around the halfway mark, for two reasons; I like to see it above half - and I've also been caught short trusting my gauge by assuming that at 1/2 a tank, I've got at least another 100 miles to go.

[moonvan]

I've done 13.2 and been literally on fumes when I got to the gas station so id be amazed if someone managed 15 gallons.

[gmushial]

Quick question for ya'll.

I understand the Z3M to have a 13 gallon tank with a 2 gallon reserve. (give or take a little)

I find on the gauge from 1/2 to empty goes real fast. But from full to half goes pretty regular.

Today I rolled in to get some gas just as I got to the half tank mark on my gauge. It took 10.37 gallons - ($44 in these parts)

Two part question:

Is it 13 + 2 (15) or 13 including 2 for reserve?

Do you all have a similar experience with your gauges? (Assuming you have the gauge that actually goes to full - this is my first Z3 that actually goes to full. The others only ever went to 3/4)

Out of habit I always tend to fill up at or around the halfway mark, for two reasons; I like to see it above half - and I've also been caught short trusting my gauge by assuming that at 1/2 a tank, I've got at least another 100 miles to go.

I don't know what the actual capacity of the tank is... but I thought it came from this forum: that the gauge intentionally "lies" to save the owner from major expenses, ie, the cost of running the fuel pump dry vastly exceeds the benefit of running it a few extra miles.

And yes, I've seen the same effect: go from just over a 1/4 of a tank to the red light on in 20 miles [and this is a mild-mannered 2.5L on the freeway doing 70]. But even with the red light on, I've never put in more than 12 gals. It might be educational to run until the redlight comes one, and then pump the tank dry and see how much in fact was still there. My guess is at least a gallon, probably more.

----- followup post:

Found this 2004 thread on the same topic... though had to laugh about $35 filling a 20+ gallon talk in a 944...

http://forums.bimmerforums.com/forum...+tank+capacity

the claim there is 13.1 + 2.1gals

[Kyle Anderson]

The reason for the discrepancy in the gauge is due to the shape of the fuel tank. About 2/3 is above half and 1/3 is below.

http://realoem.com/bmw/showparts.do?...05&hg=16&fg=05

[LAWLence]

Total capacity is around 13.25 gallons. I've run out of gas a couple of times because of the wacky gauge, so I can tell you with certainty.

[gmushial]

The reason for the discrepancy in the gauge is due to the shape of the fuel tank. About 2/3 is above half and 1/3 is below.

http://realoem.com/bmw/showparts.do?...05&hg=16&fg=05

Total capacity is around 13.25 gallons. I've run out of gas a couple of times because of the wacky gauge, so I can tell you with certainty.

And combining the two posts: it looks like the capacity is... 50 liters, or for those on the other side of the pond: 50 litres. 50 liters/litres converts to 13.2086 US Gallons (according to google).

Total capacity is around 13.25 gallons. I've run out of gas a couple of times because of the wacky gauge, so I can tell you with certainty.

13.25 is only good to three significant figures... not bad, not bad

[moonvan]

Another thing I found is if you are low on fuel/fuming the pickup appears to be in the back of the tank so going up hill will get the last of the fuel ti the pickup and going down hill will cause it to flow away.

[SNR727]

The reason for the discrepancy in the gauge is due to the shape of the fuel tank. About 2/3 is above half and 1/3 is below.
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Well that seems like about what I'm seeing. If 10 gallons is from Half to Full on the gauge, whatever's left in their would be about a third. Thanks

I've never run the car dry, but knowing this bit I'll continue my diligence of filling up closer to halfway when I'm on the long trips for sure.

I just wondered if other owners found it was like a 50/50 split and if their gauge felt really accurate or not. When I had my 2.5 it would only go up to 3/4 so I always just knew I'd be looking for gas around 250 miles or so. One time I think I got pretty close to 270 before I chickened out and refilled. (Driving from San Rafael to Palm Springs, and it was getting late - I didn't want to find myself walking through the desert looking for gas.) based on what i'm hearing here I must have rolled into the gas station on fumes without even knowing.

[ssbuchanan]

My gauge is inaccurate - it only ever gets up to about (max) 1/2-3/4 full, but it's a known issue

[SNR727]

Suddenly I'm very curious how many Z3's made it to Australia. They've got to be pretty uncommon right?

[ssbuchanan]

NFI, however, the Z4 peaked (I believe) at about 460 units per annum in Australia, so if you say maybe 500/year for the Z3, over a span of say 7 years, maybe under 4000.

The Coupes are rare as hen's teeth - I've never seen one on the road, and have finally found one for sale - I'm VERY tempted (convincing the wife we need 3 cars is another matter altogether).

The Roadsters are fairly uncommon too, I know of maybe 8 around in say a 50km radius, and I'm yet to see an M Roadster or Coupe on the street...

[dreamrider01]

For what it's worth; every vehicle I have or have had shows the same accuracy problem, which seems to become more acute as the vehicle becomes older. The further down the gauge, the faster it seems to race to the empty mark. I can only speculate that this phenomenon is electronics derived.

Question: I guess I missed it in the post, but why only fill to half tank?

[rboehl]

I have had 3 Z`s with 2 of them M`s and they all act the same. Drops like a rock after half so you gotta pay attention and get some gas. I think it is a poor design as the gauge could be calibrated correctly regardless of the tank dimensions.

[SNR727]

Question: I guess I missed it in the post, but why only fill to half tank?

That could just be a misunderstanding. I always consider the half-tank mark 'empty' and fill up every time it gets down to around half a tank. My thing about it was, that when I get down to a half tank, it takes about 10 or more gallons to fill it up. And being a 12 gallon tank... how could 10+ gallons be half?

rboehl - I agree. No excuse for that. I'm glad I'm not alone in the experience, but disappointed with the issue. Seems like such a simple thing to do. When the tank is on 1/3 the gauge reads 1/3. I mean, why not?

ssbuchanan - I couldn't imagine a world without Z3's (coupes and roadies) populating the streets and windy back roads. Here in California these cars are practically coming in the windows.

[osborni]

The gauge sender assumes a linear measurement, while the tank it tapered.

(approximate from observation)
Gauge Tank
4/4 4/4
3/4 7/8
2/4 3/8
1/4 1/8
0/4 well, then you are walking.

I routinely get ~60-80 miles on the 1st 1/4 tank, then about 120-140 miles on the rest of the tank (IIRC - or something like that).

Fixing this requires an aftermarket computer solution. Too expensive for a parts bin car.

[nine9six]

So does this mean that since the car drove off the dealers lot, the gauge have been inaccurate?

[ssbuchanan]

ssbuchanan - I couldn't imagine a world without Z3's (coupes and roadies) populating the streets and windy back roads. Here in California these cars are practically coming in the windows.

Makes sense with the weather, and the relatively high sales volume over there. Here it just makes them that much more special

On the fuel gauge issue, I just go by the OBC telling me how many more kilometers are left... I have a threshold of filling up when it gets below 80ish... it's safer that way, but I've taken it down towards 30 something.

[Racerman27410]

I use mileage to calulate when to get gas.....usually around 250 miles and i get about 10 gallons back in every time. If im really caning it in the mtns i drop that number down to around 200 miles.

the odometer is much more accurate than the fuel gauge.

[fuz9]

Seriously who drives around with less than 1/4 tank? I rarely see my idiot light come on. Who knows when you might get stuck in bad traffic?

[SNR727]

I swear every time I get in my girlfriend's Rover that light is on, or comes on within 2 minutes of driving - makes me crazy.

Traffic?



It's usually pretty light around here.

[dreamrider01]

Dream road on a dream day...

Fuel-wise, last week mine hit the light twice. The second time it was night in a road with no stations for a while, hence the real concern. I got to the station with the needle just one-little-red-cunt-hair (OLRCH) above the bottom line on the gauge. I pumped 11.623 gals in it. I doubted that the OLRCH would have gotten me further than 20 miles. Thanx to you guys now I know that when the gauge shows the needle OLRCH above the last line on the gauge I have about 30 miles of fuel left, instead. :-)

Oh! Sorry I just realized this was a M's thread. Mine isn't.

[Scarceas]

I have only had mine for a few weeks, but it does seem like the top half of the tank lasts longer.

I got 220 miles out of a tank when the light came on, and that was trying to "be good". Light came on yesterday around 205 miles (this time, "be good" meant try to keep it under 4K rpms until the oil temp was up). It only took 10.3 gallons to fill it up (about $41 for 93 octane, no ethanol). I do think the fuel light comes on kind of early, but I prefer that to running out!

[SNR727]

Where's that 93 octane at? Us Californians seem to be relegated to only 91, unless we drive up to the track, or there's that little station on the corner in Pasadena with the Hunny (which would take me about a tank to get there and tank to get back).



I've never put the track gas in my car because I've heard it's havoc on the cats.

[dreamrider01]

Where's that 93 octane at?

Kroger (nation-wide supermarket chain) fuel has it in all their gas stations in NC. Dunno 'bout CA. Actually, now that I am looking for 91-93, it seems most premium fuel around here (my house) is 93 octane (about $3.85/gal).

[SNR727]

I never understood how gas gets priced. We're at about $4.30 a gallon here today for 91.

I know it's better than LONDON, but still. I'd like to see it kind of the same (lower) price across the country. We can see a 30 to 40¢ swing per gallon in a 30 to 40 mile radius.