There is no return line to the tank in the FEH. It keeps the correct fuel pressure by adjusting the duty cycle of the fuel pump.

 

I hate this about the vehicle, and I go through this all the time.
Once, I would add .25 than rock the vehicle, then another .25 gallon, then rocked the vehicle, and I got 17.5 gallons in there. Really!
And I have a standard 2005 FEH.

So there is AT LEAST 2.5 gallons of air space.
I just had to drive over 800 miles in one day.
I wanted to stop for gas once, not twice before getting home.
So I made sure to "rock" the car.
I wasn't empty when I started, so I didn't pump 17.5 gallons, but I put in at least 2.5 gallons past the "first click". That's 75 extra highway miles. Close to 100 extra city miles ( for me ). -J

P.S. All the time I see posts about people who are pleased to get 400 miles per "tank". I regularly get over 500 miles per tank, and a few times, over 600 miles. I'm sure this method of filling-up would help most of you get 500 miles per tank also.

 

there's usually some space in the tank and in the filler neck- but wow- 2.5 gals seems a little wild that you can pack that much in. You sure know how to top that baby off- LOL.

The gist I've gotten is that if one is gonna drive a bunch than there's no harm to packing it in. The only time one could really get into trouble is if you fill it to the brim and then let it sit in the sun or (on older cars with the fuel return line- if you let it idle). Otherwise you use up some fuel and make space for expansion and it all works out (although with the FEH it might take a few hours of driving to use up that 2.5 extra packed in gallons?) .

I think the new gas station pumps are part of it. But I also think some of it is over reaction from the car manufacturers from the dual tank pickups in the 70's and 80's. Those had all sorts of tank problems- and one of them was overpressurizing one tank or the other (for reasons that really have nothing to do with modern vehicles and certainly not the FEH) . So might just be like the stupid GPS nags screens of today- some lawyer freaked out and tells the car manufacturers they better leave lots of air space in the tanks to avoid those old issues.

 

Ford and other manufactures have gone to a single line fuel delivery system, no return to tank. The Ford system uses a varible speed computer controled electronic fuel pump in the tank.

 

The air space is required for the evaporative emissions system to function properly. Evaporative emissions is increasingly important because the combustion/catalyst process is so clean with modern engines.

 

figured there must be a logical reason.

If you "overfill" the tank does it cauase damage? Or just produces more emmisions?

 

Just to the paint, and to your pants.

 

I think thats true. Its also likely that the reason gas pumps shut off so soon is they are made more sensitive than in the past, so they will kick off earlier and not overfill so there is no spillage of gasoline... We live in a sue happy society.

 

I notice more often than not that gasoline "foams" almost like soapy water when you fill fast. I think people who do fill at full speed, and then get a "click off" 1.5 or 2.5 gallons early are getting a filler tube full of foam and that foam backs up the nozzle and shuts it off.

Wait 30 seconds after "first click" next time to allow the foam to settle, and then fill at the slowest speed possible after that, I'll bet you a box of donuts you get at least another 1.5 gallons in. Maybe more.

Will this help MPG or hurt anything? No, and no.
However, you may get to wait an extra day before refueling... adding up to 1 or 2 fewer trips to the pump per year!
-John