From time to time, you come across a gas bar with lower than average gas price, and feel the greed to top up a little more than where the pump stops on it's own when it senses a full tank.

By forcing an additional gallon or so (without over flowing), does this have any long term effect - damage - to the gas tank sensors?

Not that I'm aware of!

Not that I'm aware of!

May be it's a GMC thing as I was told by the GM dealer that is the reason for my persistent engine light indicator being lite up.

Hopefully, the superior engineering of the Armada is able to avoid such a simple issue.

I was always told that exceeding the gas tank limits will block a breather valve which can cause stalling. Kind of like leaving your finger on the top end of a straw and the fluid stays in the straw until you take your finger off of it.

Phssshhh Hogwash..... I always top it off rounding up to the next whole $.50 mark.. Put as much as you want in there, overflow it if you feel the need to, you'll be fine as long as the EPA doesn't get involved with a spill. :D... It's been done on all makes and models for over a century and is no different than overflowing your lawn mower....

I have done it since we bought it and with my other cars, rounding off to the next .50 to 1 dollar, and have never had a problem with any of them, mind you they are all nissans, I don't do it with my daughters Equinox (not my idea guys, they have been taken off the will :) ) problem now is I have to pay twice to get it to that point. Our pumps shut off at $75, which means you have to start over again, and 75 dollars at $3.81/gal does not get you far the first time around.

I checked with my mechanic, and was informed that topping up a gallon or so more after the initial "full" is bad for the sensors. I was advised against topping up more than a couple cents to round up to the nearest dollar.

The gas prices are Crazyyy.Eversince i bought my mada i put supreme 93 and last nite i had 2 gallons left in my tank and i decided to fill it full on I-87. supreme was at 3.84 per gallon. It took 85 dollars to fill it up. I was stunned. If gas prices keep goin up i'll need 100 bucks to fill it up. The escalade that i had in 05 needed $90 to fill it up. But even if prices go at $5 per gallon i aint selling my mada eitherway.

After reading this I stopped doing it. I didn't like the idea of giving the gas back to the station:

http://www.epa.gov/donttopoff/

And if the goverment says it must be true! :p

The gas prices are Crazyyy.Eversince i bought my mada i put supreme 93 ~~~.Use 87 not 93.

I've tried lesser grade gas (even 89) and everytime I idle, it's rough. Very scary. Feels like it's going to conk out. It'll be embarrassing to have people help you push (is it even possible?) this truck to the side?

So, I now never fuel up with nothing less than a 91, and never at a no name station.

I always use either Shell or Mobil premium grade and usually top off to the next dollar.

I have always experienced great performance using 87 for the past 5 years. I guess fuel quality may be different from place to place if you guys are experiencing sluggishness and stall outs.

Do what is best for you and your vehicle, nobody knows it better than you! :D

I have used 87 octane since I got this le a year ago february. I get comments about how it sounds and runs and they are in disbelief when I tell them that this is stock. Run great on 87...

[QUOTE=BlakSpyda;176224]Use 87 not 93.[/QU

why 87? isnt 93 better? i never put any other grade except 93 eversince i bought it. Some say 87 makes it sluggish and i dont even wanna try it bcus for a few cents it doesnt hurt my pocket but if performance is the same with 87 then i'll go with 87.

[QUOTE=BlakSpyda;176224]Use 87 not 93.[/QU

why 87? isnt 93 better? i never put any other grade except 93 eversince i bought it. Some say 87 makes it sluggish and i dont even wanna try it bcus for a few cents it doesnt hurt my pocket but if performance is the same with 87 then i'll go with 87.

Higher octane fuels are only better if your motor is designed for them. The VK56 is designed to run on 87. 93 octane fuel is designed to be more resistant to ignition than 87, meaning it's harder to start the burn process. This is beneficial in high compression motors, it lessens or eliminates any harmful knock or ping. Our motors were designed around 87 octane fuel. They won't knock or ping on 87. Putting 93 in them is a waste of $ unless you're towing an 8000lb trailer on a 90 degree day.

Higher octane PUMP fuels can actually have less energy content per gallon that 87. Often, ethanol is used to raise octane numbers in gas. Ethanol has a lower energy content than gas. So the more ethanol you're pumping into your rig, the less hp it will put out:D

I use 93 octane due to the 2* timing advance on my Armada.

[quote=bigerv;176260]

Higher octane fuels are only better if your motor is designed for them. The VK56 is designed to run on 87. 93 octane fuel is designed to be more resistant to ignition than 87, meaning it's harder to start the burn process. This is beneficial in high compression motors, it lessens or eliminates any harmful knock or ping. Our motors were designed around 87 octane fuel. They won't knock or ping on 87. Putting 93 in them is a waste of $ unless you're towing an 8000lb trailer on a 90 degree day.

Higher octane PUMP fuels can actually have less energy content per gallon that 87. Often, ethanol is used to raise octane numbers in gas. Ethanol has a lower energy content than gas. So the more ethanol you're pumping into your rig, the less hp it will put out:D

Thank you rotomoto :bow: I guess I will go with 87 then. Welcome to CA!!

Welcome to CA rotomoto

I use 93 octane due to the 2* timing advance on my Armada.

I have 2° Timing Advance and use 87 octane. I get to race and blow away many vehicles to their driver's dismay and surprise!



Use 87 not 93.

why 87? isnt 93 better? i never put any other grade except 93 eversince i bought it. Some say 87 makes it sluggish and i dont even wanna try it bcus for a few cents it doesnt hurt my pocket but if performance is the same with 87 then i'll go with 87.

What rotomoto said! ;)

2* Timing Advance does not require a higher Octane. I run it, and an UpRev Tune all the time for 5 years now. All is fine. It is also within factory Specs for Timing.

A recent feature on the MD PBS show MotorWeek Magazine illustrated the actual damage to sensors, causing them to have to be replaced. I'd like to see that episode again to learn more though. The overflow clogged a breather for fumes from the Intake Manifold or something like that, an emissions control device.

I was always told that exceeding the gas tank limits will block a breather valve which can cause stalling. Kind of like leaving your finger on the top end of a straw and the fluid stays in the straw until you take your finger off of it.
Our fuel delivery system and that of many other fuel injected (and some carb'ed) vehicles circulate the fuel from the tank to the fuel rail where the fuel pressure regulator sends the excess back to the tank, there's nothing to really block. The system is almost sealed. Proof of this is sometimes when you're opening the fuel filler cap you can hear the pressure in the tank escaping. We do have a fuel charcoal canister that captures fuel vapors but that's *mainly* the vapors that don't get pushed out the tank when you fill'er up ;) .

I fill it till it clicks, then pull the nozzle back and top up till I can hear the fuel coming up the filler neck (you know the sound). I try not to let the fuel get to the actual nozzle because I've read that it can circulate back into the nozzles vapor catchment thing-auh-ma-jig. I'm going to write Myth Busters on that one though lol :D .

Here is my experience... a little easier since I live in Western Colorado and there is no vapor return hose to make the process more difficult (no emissions regulations require them). I fill until there is fuel visible in the neck. I then allow that to settle... maybe 15 to 30 seconds. I then top it off again by allowing just a trickle to flow from the pump, again until there is fuel visible. It takes 6-10 times to actually get the filler neck to the level that the fuel will no longer settle into the tank. I should add that I also never spill a drop or allow any fuel to get on the paint. Nothing is returned to the hose since I do not place the pump dispenser into the neck while topping it off. You can generally get about 2 more gallons into the tank beyond the point where the pump will automatically shut off with the filler stuck down into the neck.


ALSO-- it is important to be very gentle when placing the dispenser into the neck as they are both soft metals and small shaving can be scraped off which will be washed down the neck with fuel and eventually make it to your fuel filter.