thefisch

With every car I've owned, the owners manual and fuel cap has said not to top off the fuel tank. However, I've always ignored those warnings (along with some others in life) and tried to add extra fuel to add a little more time/distance between fill ups. With past cars (non-MB), adding another 0.5-1.0 gallons after the pump nozzle clicks off was never an issue.

While I am only on my third tank with MY11 E550, I have not been able to add hardly any fuel at all the pump clicks off. Maybe 0.2-0.3 gallons after several attempts. This has been at different stations that I've used and been able to top off successfully on past cars.

Perhaps the MB fuel receptacle is different. Heck it looks different than past cars since it has a plastic guide for the nozzle instead of the typical metal opening.

Any ideas?

dfordham

I've heard that topping off the tank can, over time, cause problems with the charcoal canister in the vapor recovery system. It can get clogged which makes it difficult to pump in the gas.

Oh, and it also costs $500 to replace.

Regards,
Don

BenzV12

Oh my God , I always have it topped off .Thanks for the heads up
It seems then neither last dregs of fuel nor topmost fuel is good

alanme123

I've been doing it for like 2.5 years on my W212 now.. I guess its time to stop haha. It's satisfying to fill up 20 gallons..

DeanBee

I have a 2014 E250BT diesel, and one of the first items the dealer told me when I picked up the car was to not top it off as it will set off the "Check Engine" light on the Bluetec. Since I live 300km from the dealer (who resets the check engine light) I have followed his recommendation! I usually pay by debit so paying 34.57 instead of rounding up isn't a problem.

YYZ-E55

Wise (and accurate) words.

thefisch

I've heard the same thing about the vapor recovery system and canisters on other brands but have never come across anyone who has had a problem or had to repair it. Don't get me wrong - I don't try to fill it up so it is overflowing [Although I did have a Prius that spit/sprayed gas out if you tried to add more than 0.5 gallon after the pump clicked off. That's a story for another forum though.] I am just trying to squeeze as much between fill ups as possible. Also, my crazy logic makes me think it helps with accuracy of actual mpg calculations since you are not relying on some random service pump handle to decide when your tank is full.

But back to the main inquiry. For those of you brave souls that do top off, how much more are you able to add after the pump first clicks off?

benyl

Are you aware that the volume of fuel changes with temperature?

thefisch

Yes, but here in FL the temperature doesn't change - it is always hot.

mbuster25

I do not top off in the typical sense, but I try to slow down the pump by pressing a lot less (1/4-1/2) than full towards the end

El Cid

I've heard that this is actually another internet rumour.
I set the pump handle for the slowest feed and wait for it to cut off. Then I gently hold down the handle until it stops. At that point I quit.
BTW, I've heard that you should not let tank get below 1/4 anyway, so will a few ozs. really help. Apparently, below 1/4 you might get sludge from tank or water from the ethanol. Also, in really cold weather, the water in the ethanol may freeze if tank is near empty.

benyl

I guess the Government of Canada is in the internet rumour business.

http://www.ic.gc.ca/eic/site/mc-mc.nsf/eng/lm04344.html

The NIST thinks so too:

http://www.nist.gov/pml/wmd/pubs/upl...nual-final.pdf