N 51 fuel gauge and consumption question

[chalupa2000]

I'm noticing that the fuel gauge reads down about quarter tank having traveled about 65miles from full fill of the tank. Average mpg seems normal based on obc. Is this what others see on their fuel gauge activity? Coming from an e46 for me seems like the gauge isn't calibrated correctly

[Suprgnat]

Originally Posted by chalupa2000

I'm noticing that the fuel gauge reads down about quarter tank having traveled about 65miles from full fill of the tank. Average mpg seems normal based on obc. Is this what others see on their fuel gauge activity? Coming from an e46 for me seems like the gauge isn't calibrated correctly

14 gallons / 4 =3.5 gallons. 65 miles / 3.5 gallons = 18.6 MPG. Sounds about right for around town. You didn't mention what your MPG was.

[chalupa2000]

Thanks for the input and response... I haven't been able to drive it consistently but when I check the obc it shows 21mpg (if I were to average what I recall 17 to 28mpg depending on when I check...)

[SayHack]

All i know is when i was younger I did a drive 270 miles roundtrip (cruising at 75mph) about 10 times over a 3 month period, and every single time i had 1/3 tank left like clockwork....but to clarify something, the gauge only shows 1-14 gallon mark (so if its showing dead zero , if means there is a gallon of reserve left). so for the math above, its 13/4 = 3.25 gallons.....so 65miles/3.25gal = 20mpg (not that it makes a huge difference but just being technical)

[Suprgnat]

Originally Posted by SayHack

All i know is when i was younger I did a drive 270 miles roundtrip (cruising at 75mph) about 10 times over a 3 month period, and every single time i had 1/3 tank left like clockwork....but to clarify something, the gauge only shows 1-14 gallon mark (so if its showing dead zero , if means there is a gallon of reserve left). so for the math above, its 13/4 = 3.25 gallons.....so 65miles/3.25gal = 20mpg (not that it makes a huge difference but just being technical)

To be really technical, the fuel reserve is 2.1 gallons (8 liters). My low fuel light comes on pretty much at 12 gallons gone, plenty of warning, but I don't hit zero on the gauge until I'm really out of fuel. Just a few weeks ago I was showing 6 miles-to-empty, the gauge was hovering just above the empty line, and I put in 13.6 gallons of gas. At least in my car, empty is empty.

[SayHack]

Originally Posted by Suprgnat

To be really technical, the fuel reserve is 2.1 gallons (8 liters). My low fuel light comes on pretty much at 12 gallons gone, plenty of warning, but I don't hit zero on the gauge until I'm really out of fuel. Just a few weeks ago I was showing 6 miles-to-empty, the gauge was hovering just above the empty line, and I put in 13.6 gallons of gas. At least in my car, empty is empty.

Interesting.

I have driven my car with range showing --- (which for my car happens when its less than 2 miles). I have done this few times over the years, not my proudest moments. I don't remember exactly how much i filled up, but im pretty sure it was very close to 13 gallon mark. Maybe there is something wrong with my gauge lol. Actually other than these few exceptions where I was "completely empty", I don't ever remember filling more than 13 gallons, it's usually 12.6-12.7 gallons when my gauge is only 1 lines over the empty. Again might just be my car.

[smeard]

Originally Posted by chalupa2000

I'm noticing that the fuel gauge reads down about quarter tank having traveled about 65miles from full fill of the tank. Average mpg seems normal based on obc. Is this what others see on their fuel gauge activity? Coming from an e46 for me seems like the gauge isn't calibrated correctly

Pray you never have to replace the tank or related equipment, it is a ~$7k bill to replace out of warranty. Glad warranty is 15 year/ 150k mi. But that fuel usage sounds about right, I have noticed my car goes thru fuel significantly faster below half tank than above.

[chris_flies]

I've found my fuel gauge to be very accurate, especially compared to my dad's Mk7 GTI; it doesn't display how much fuel you have, but how much range you have. So, on the track, it may display as empty, but he still has 4-ish gallons in the tank.

[chalupa2000]

Thanks for the input everyone... I noticed at certain gas stations or pumps my overfill click would kick in prematurely needing me to reposition every few seconds... Only happens on certain pumps that could cause me to not fill up top off all the way. Anyone else have this happen and know the cause

[chris82]

N51 owner here. my fuel consumption on the highway is consistently close to 30 mpg no matter how I'm driving it, around town i'm looking at low 20s. I'd say 18 is pretty terrible unless you're mashing the throttle down all day. Also, when my low fuel light comes on, I have EXACTLY 1 gallon left. I've confirmed this multiple times. It's pretty damn accurate!

[Suprgnat]

Originally Posted by chris82

N51 owner here. my fuel consumption on the highway is consistently close to 30 mpg no matter how I'm driving it, around town i'm looking at low 20s. I'd say 18 is pretty terrible unless you're mashing the throttle down all day. Also, when my low fuel light comes on, I have EXACTLY 1 gallon left. I've confirmed this multiple times. It's pretty damn accurate!

I don't know how you do it. Before I got the 3.64 diff I could only get 30+ on a long trip if I nursed it, 28+ if I nurse it with the 3.64. I get mid-18s daily (regardless of diff ratio), non-highway, and have managed a few mid-10 MPGs.

I may need to have my right foot examined.

[Suprgnat]

Originally Posted by smeard

Pray you never have to replace the tank or related equipment, it is a ~$7k bill to replace out of warranty. Glad warranty is 15 year/ 150k mi. But that fuel usage sounds about right, I have noticed my car goes thru fuel significantly faster below half tank than above.

N51 fuel tank is only $795. E46 325i SULEV tank is $8079.58 at bmwminipartstore, which is a tad more than $7k

[smeard]

Originally Posted by Suprgnat

N51 fuel tank is only $795. E46 325i SULEV tank is $8079.58 at bmwminipartstore, which is a tad more than $7k

Huh I heard it was a lot more than that. Maybe we got lucky:

[smeard]

i get around 17 in city (but I drive wuite enthusiastically) and anywhere from 23-28 on highway

[Suprgnat]

Originally Posted by smeard

Huh I heard it was a lot more than that. Maybe we got lucky:

BMW learned from the E46 debacle.

[chris82]

Originally Posted by Suprgnat

I don't know how you do it. Before I got the 3.64 diff I could only get 30+ on a long trip if I nursed it, 28+ if I nurse it with the 3.64. I get mid-18s daily (regardless of diff ratio), non-highway, and have managed a few mid-10 MPGs.

I may need to have my right foot examined.

Sounds like you're getting better highway mileage than me. I've never gotten into the 30s even ONCE on the highway, but I honestly can't remember i was below 20 mpg. I would really have my foot down for that to happen.

[JimD]

My overall mpg is about 28. The gauge shows 28 but my spreadsheet from actual fillup data is a bit lower.

I normally get a bit more than 100 miles before getting to 3/4 tank, then about 100 miles before getting to 1/2 tank and maybe another 70 before getting to the 1/4 mark. Then I get the light at around 300 miles. On a trip, this goes up. If I put my foot in it too many times, it comes down. The gauge is thus not totally linear but is reasonable. It probably has something to do with the gas tank shape.

[SayHack]

Originally Posted by JimD

My overall mpg is about 28. The gauge shows 28 but my spreadsheet from actual fillup data is a bit lower.

I normally get a bit more than 100 miles before getting to 3/4 tank, then about 100 miles before getting to 1/2 tank and maybe another 70 before getting to the 1/4 mark. Then I get the light at around 300 miles. On a trip, this goes up. If I put my foot in it too many times, it comes down. The gauge is thus not totally linear but is reasonable. It probably has something to do with the gas tank shape.

You know I am not sure if I can follow that....for my car it seems as if from full to 1/2 mark it drops faster than from 1/2 to empty. Anyone else experience that or just me ? lol

[JimD]

I get 200 miles pretty consistently before hitting the half full mark. I have never gone 400 miles on a tank so mine is going slower in the first half of the gauge. I get 100 miles for the first quarter tank (or a bit more), another 100 miles for the second quarter tank, then about 70 miles for the third. I fill up before going another 70 miles on the last quarter tank, at least I usually do.

Thinking about it right now, I go about 30 miles before I get to the "F" mark on the gauge after a fill-up. If you factor that in, It is closer to 70 miles per quarter tank.

[chris_flies]

Originally Posted by chalupa2000

Thanks for the input everyone... I noticed at certain gas stations or pumps my overfill click would kick in prematurely needing me to reposition every few seconds... Only happens on certain pumps that could cause me to not fill up top off all the way. Anyone else have this happen and know the cause

In case you're still looking for an answer, it's likely the charcoal canister located behind the rear bumper. It's an emissions device, and is likely replaceable under the 15yr/150k-mile SULEV warranty if it is indeed the problem.

[Gweeper64]

Originally Posted by SayHack

You know I am not sure if I can follow that....for my car it seems as if from full to 1/2 mark it drops faster than from 1/2 to empty. Anyone else experience that or just me ? lol

Originally Posted by JimD

I get 200 miles pretty consistently before hitting the half full mark. I have never gone 400 miles on a tank so mine is going slower in the first half of the gauge. I get 100 miles for the first quarter tank (or a bit more), another 100 miles for the second quarter tank, then about 70 miles for the third. I fill up before going another 70 miles on the last quarter tank, at least I usually do.

Thinking about it right now, I go about 30 miles before I get to the "F" mark on the gauge after a fill-up. If you factor that in, It is closer to 70 miles per quarter tank.

The behavoir of mine matches those almost exactly. I've also found after a fill up, the range estimate is a little bit optimistic and I get maybe 5% less than the estimate at fill-up time. I'm not complaining though. I can typically go 330 miles between fill-ups. More on a long road trip.