OBC maxes out at 54 liters?

[nando]

Does this make any sense? I have the 64l tank. 99% sure the OBC has the right coding plug as it came from my '88 ix parts car. Also, when I subtracted how many liters were left before I filled from how many it said after, it matched exactly with how much I put in the tank (~12.4 gallons). The tank is definitely full. I wasn't at the reserve light yet.

if it says 54 liters when full and it goes to "0" at reserve (6l left) it sort of makes sense but not really, there's still 4l unaccounted for. is that on purpose? on newer BMWs the tank is also ~64 liters but the gauge only accounts for 60l (technically, 57 + 1.3l safety factor) and the reserve light comes on at 8 liters.

[bmwstephen]

I think this is pretty common chris. this issue has been brought up a number of times. I've replaced both fuel level sensors and nothing changes. the tank is dented either. I just suppose it's how the system was evolved from the dual pump setup in the pre-facelift models. My yellow light comes on after 11.5 gallons and by the time I fill it up, I was wondering why it can't take in the additional 4 gallons like it should

that said, I'm wondering if that is the reason my car gets crappy mpg as indicated by the OBC. Does it take into consideration the tank size?

[nando]

No, its based on injector pw vs distance travelled.