My 2016 JCW is listed as having a 11.6 gallon tank...

I have filled up 11.7 gallons before, 11.4 and 11.2. Different gas stations as well... is this tank truly 11.6? or is it slightly bigger, the car thought there was range left at all of those fill ups.

Every single car I have owned before, once seeing 0 indicated range would have 1-2 gallons left in the tank.

 

Never have I pushed any car to see just how low I could run the fuel level and what the subsequent amount of fuel required to refill the fuel tank would be.

Every once in a great while -- but not with the JCW -- I have run the fuel level pretty low. For a car with a claimed 16.9 gallon fuel tank I once put in 15.6 gallons.

In the case of your car, it is possible that at some point during the production run the tank capacity changed due to a redesign of the tank or a switch to using a different supplier with a slightly different tank capacity and your car has a tank with more than the published capacity.

There is the question of how accurate the fuel pump measuring system is. This is really no different than the weigh scale at the local butcher shop. It needs to be checked. A number of states have cut way back on checking gas station pumps for volume accuracy. Even assuming there is no tampering of this being done by the station management/employees it would not surprise me if as the volume measuring hardware went out of adjustment that it would tend to be in favor of the station not the customer.

Depending upon how much trouble one wants to go through it is often possible to "squeeze" some "extra" gasoline into the fuel tank. The nozzle shut off of course stops the flow of fuel before there is any real risk of overflow/spillage.

With my JCW a few times I have done this I managed to just restart the fuel flow, albeit at a lower flow rate, after the nozzle shuts off and get nearly a half a gallon "extra" fuel in the tank and yet not see any signs of fuel spillage. Were I inclined I might be able to get maybe not another half gallon but portion of a gallon more fuel in the tank if I went to the trouble to fill the tank to the brim of the fuel tank fill tube.

However, it is not advisable to fill the tank too full as this can interfere with the fuel ventilation system, possibly even putting raw fuel in the charcoal canister which can ruin it.

There have been cases where the system that is used to shut off the fuel flow when the tank gets full actually can pull fuel out of the tank. There have been cases where the driver of the vehicle after unattended filling of the tank found the amount of fuel pumped was quite a bit over the fuel tank's published capacity. The automatic shut off system was suspect. (It could also be possible that if the driver of the vehicle was totally oblivious to the situation a driver of another vehicle on the other side of the pump moved the nozzle to his vehicle's tank for a quick few gallons of "free" gasoline.)

 

It's also a good way to burn up a fuel pump. And, as an aside, old pilots prefer to burn off the top half of the tank, that based on lousy outcomes of less cautious pilots.

 

This is often stated as a concern and it has some validity. I put a lot of miles on a number of cars including one I drove to 317K miles. While I didn't run the fuel level down real low -- with a few exceptions -- the level got down to 1/4 tank or even less. The fuel pump died at around 200K miles. I do not think that even though I ran the tank as low as I did albeit 1/4 tank (around 4 gallons) that this had any real impact on the fuel pump's service life.

My other car's fuel pump quit at around 120K miles and I seldom let the level get to 1/4 tank. This car had a saddle tank -- to clear the front AWD diff -- and used siphon jets to pull fuel out of the two unconnected -- at the bottom -- basins. The fuel pump just had to work harder and as a result this contributed to its shorter service life. Because the fuel pump I felt had to work harder I tried to keep the fuel level higher to provide a larger volume of fuel to help keep the pump cooler.

This car also came equipped with a fuel cooler -- which was "active" with the A/C was on -- which I think was an admission fuel temperature was a concern.

I am not familiar with airplane fuel systems.

With modern cars the fuel tank contents are pretty well stirred up all the time. The fuel pump is designed so some of its output is routed back to the tank in such a way that fuel pump is kept doused with fuel to help keep the temperature down. At the same time this continuously stirs the fuel in the tank to avoid any stratification of the fuel.

Thus I have no qualms about running the fuel level 'low" in a car other than a mild concern about the pump possibly being subjected to slightly higher operating temperature that it might otherwise be subjected to. But not enough to cause me to change my ways.

 

"top" half of tank would mean filling up every 120 miles, no thanks. I am not going to the gas station every other day.

 

That's figuratively speaking. I always calculated an extra 1/2 hour fuel on flight planning and was damned sure to have an alternate field available en route. Yet, on road trips, I'm looking for a source when reaching about 250 miles...or sooner depending upon my co-pilot's needs, wants and/or desires.
One rule of thumb still applies, and I quote: "There are old pilots and there are bold pilots. But, there are no old bold pilots."

 

Since were flying in the streets when the light comes on there is another 1.5 hrs of drive time at my average speeds. So it sounds like I’m safe.

 

Well said and thank you for a good chuckle.