Running on Empty/Accuracy of Low Gas Dash Warning

Sounds like your car has the early fuel sender unit. Early cars have a fuel level sensor in the fuel tank on the drivers side that has a float in it that only goes so far before it hits the side of the tank, thus the 3/4 "full" level on the gauge. There is a replacement that entials removing the float fuel pump assembly and installing it. There are a few threads about this sorry I can't remember the link offhand. It's one way that I knew my 99' had been loved and updated in the past, with the new level sensor it shows full. As I understand it it is triggered by the signal from the fuel tank sending unit.
I don't see how this would affect the "lower" fuel levels in the tank. I would take the low fuel level as "accurate".

 

I have wondered that same thing on the cars I own. I think the best way to tell is to see just how much it takes to fill it up at that point, and then subtract from the fuel tanks' capacity. The difference is how much you actually had remaining. All but one of the cars I have had contained much more fuel than indicated. I think it's the mfrs way of keeping us from running out.

ps. The one guage that was dead accurate was my 308. I ran out as I was pulling up to the pump!

 

I can't remember where I read it but I seem to recall a +1 liter excess factored into the system for the safety reason..

 

I don't know a whole lot about how these new Ferraris are set up fuel wise - but based on my experiences with other fuel injected cars I STRONGLY advise that you keep the tank at least 1/3 full at all times.

First - fuel injected cars hate running out of fuel. Or even trunning very low on fuel. Doing so can cuase problems.

Also, on FI cars the fuel pump - a massively high pressure thing that bears no relationship with the pump on a carb car - is typically mounted inside the gas tank. The fuel is used to cool the pump. Running low on fuel will reduce the life of the fuel pump.

Running with full tanks costs no more than running on empty. The amount of gas you use is the amount of gas you use.

I recommend filling up when you are down to 1/3 full.

 

I know my fuel guage has read full before, but today it was 3 bars down when I started it, put in exactly 5 gallons, and when I turned it on it was at 2 bars down from full. Doesn't quite make sense, as I then drove 50 miles on the highway and it's still showing 2 bars down. Generally, I've felt like it has been pretty accurate but does seem to dash back and forth a bit between bars.

I'm just glad it's a BIG tank, 20 galllons + right (?), as compared to my 911 turbo which can barely take 12 gallons when on empty and I feel like I'm always having to fill it up when driving it a lot.

 

Sounds like your sending unit is bad. My car started with the same symptoms and go a little worse. I ended up changing my fuel sending unit. Wasn't that difficult. See thread below:

http://ferrarichat.com/forum/showthread.php?t=346059