[subdivisions]

Hey,
A neighbor of mine has an ultra pimped 2016 SS. He is an old-school car guy in his early 70's (says buying the Camaro made him feel 15 years younger). He has owned over 50 cars in his lifetime. Here's the debate:


He recommends that i DO NOT let fuel gauge get under 1/4 tank. He says it makes the fuel pump work harder and can lead to premature fuel pump life. I have done a little internet research (and as we all know a little internet knowledge can be a dangerous thing). MOST info i found supports the not lower than 1/4 tank thought. However i did find some other information saying that letting the fuel get low allows the the fuel filter (a cheap replacement part) a better chance of catching contaminants from the bottom of the tank. Thoughts?

[Nothing like an SS]

Well, this is an age old debate to say the least....

I PREFER to not get below 1/4 tank, mostly for many "old school" reasons that often still apply.

Low volume of fuel allows the tank to corrode more rapidly inside.
Yes, going lower sucks the crap out and through the filter, but why would you want to suck any of it up?
Also, modern in tank fuel pumps use the fuel for cooling as well, so lower volume may impact fuel pump efficiency.

Do I have evidence of any of this? No, just internet anecdotes. Although, fuel tank corrosion is real, especially in the colder temps where condensation builds up more rapidly, which could also lead to fuel having a higher water content, not optimal for burning.



Like many threads of this type on here, I am sure this will get REAL interesting! LOL

[ZED SLED]

most of today's fuel tanks are plastic if not all so corrosion won't be an issue. But along those same lines there can still be debris over time in the bottom of the tank that you don't want sucked into the pump. I still let my cars get to around 1/8 tank around town before filling up. I try to fill at 1/4 on road.

and ask you neighbor why a 1/4 tank would make the pump work harder?

[subdivisions]

Originally Posted by ZED SLED

most of today's fuel tanks are plastic if not all so corrosion won't be an issue. But along those same lines there can still be debris over time in the bottom of the tank that you don't want sucked into the pump. I still let my cars get to around 1/8 tank around town before filling up. I try to fill at 1/4 on road.

and ask you neighbor why a 1/4 tank would make the pump work harder?

I think the working harder part has to do with the pump being fully submerged in fuel (heat, fewer inlets into pump maybe) but what do i know.


But my argument is .. don't you want the fuel filter doing it's job of removing possible debris in tank? Again, what do i know.

[95 imp]

The fuel baths and cools the pump. The lack of fuel in the causes the pump to run hot/overheat and causes it to fail.

Having a plugged/partially plugged fuel filter (since it pushes fuel thru) raises the pressure between the pump and the filter causing the pump to work harder which also overheats it and causes premature failure.

[cellsafemode]

as long as the pump is not running dry, you should be fine. That varies. And so the quarter tank rule of thumb was born.

It's probably closer to E in modern cars than even cars from a decade ago since modern gas tanks do a good job at making sure if there's even 1 gallon left in the gas tank, that the pump is getting it all. I remember in my 3rd gen turning left (or right...i forget which direction) really hard could make the pump suck air if below 1/8th tank.

If you have garbage built up in your gastank, you're on borrowed time. Having fuel or not isn't going to avoid the issue of a clogged pump when that junk eventually gets sucked up.

E exists there to tell you that you are now running the risk of running the pump dry. Above that and it's still got fuel to keep it cool.

I would obviously try to never run it down to E and to not aggressively drive the car when the tank is below a quarter tank ...but i dont think you'll do any damage just noraml driving and having it get near E from time to time since modern gas tanks will keep it wet.

[UnknownJinX]

It's mostly an old wives' tale at this point since a lot of people get away with not having to replace fuel pumps after they run out of gas. That said, there are many other good reasons to not have your gas level too low - for example, inconvenience, escaping an emergency situation and keeping yourself warm if you drive a car in the cold and get yourself stuck.

Besides, our engines have DI and a lot of the compression happens at the cam shaft since DI requires a lot higher pressure. Makes me wonder how hard a DI fuel tank pump has to work compared to a PI fuel tank pump since the cam shaft seems to be doing a lot of the work already.

The only potential issue I see is the saddle shape of the tank. Mazda uses a saddle shaped design for the RX-8 and the fuel pump is on the driver side, so if you go below 1/4 tank and do a high-G left turn, you could slosh all the fuel into the passenger side hump and now you have fuel starvation. I would think GM figured this one out, though, by having some way to balance the amount of fuel on each side when the fuel level is low enough.

[ctrlz]

Originally Posted by UnknownJinX

I would think GM figured this one out, though, by having some way to balance the amount of fuel on each side when the fuel level is low enough.

Like with all manufacturers, these saddle tanks have a balancing mechanism. Keeping fuel in the tank at a certain level will only affect the primary and secondary pumps (the ones in the tank). The high pressure pump which feeds the rail is up by the engine.

Personally, I think it is a small safety measure to never let the tank get very low. Since the filters are now integral to the pump, I see no point in ever having any kind of particulates get near the intake screen. Let that stuff float or slosh on the bottom. Replacing a fuel pump is no fun. Most of the pump cooling comes from fuel moving through the pump. We have a returnless system, so hot fuel that has moved close to the engine and then returned to the tank is not an issue.

From the repair manual:

DESCRIPTION AND OPERATION > FUEL SYSTEM DESCRIPTION > FUEL SYSTEM
OVERVIEW

The fuel system is an electronic returnless on-demand design. A returnless fuel system reduces the
internal temperature of the fuel tank by not returning hot fuel from the engine to the fuel tank. Reducing
the internal temperature of the fuel tank results in lower evaporative emissions.
An electric turbine style fuel pump attaches to the primary fuel tank fuel pump module inside the fuel tank.
The fuel pump supplies fuel through the fuel feed pipe to the high pressure fuel pump. The high pressure
fuel pump supplies fuel to a variable-pressure fuel rail. Fuel enters the combustion chamber through
precision multi-hole fuel injectors. The high pressure fuel pump, fuel rail pressure, fuel injection timing,
and injection duration are controlled by the engine control module (ECM).
The primary fuel tank fuel pump module also contains a primary jet pump and a secondary jet pump. Fuel
pump flow loss, caused by vapor expulsion in the pump inlet chamber, is diverted to the primary jet pump
and the secondary jet pump through a restrictive orifice located on the pump cover. The primary jet pump
fills the reservoir of the primary fuel tank fuel pump module. The secondary jet pump creates a venturi
action which causes the fuel to be drawn from the secondary side of the fuel tank, through the fuel

transfer pipe, to the primary side of the fuel tank.

[I`m Batman]

I usually keep the tank full most of the time because sometimes I park the car for long period of time (unplanned) and don't want to fuel to go bad. Less air in the tank the better. Plus I don't like seeing my fuel gauge low in any of my cars... probably OCD or something.



... and don't get fuel when you see a fuel truck at the gas station filling the underground tank.

[VinnAY]

People can make up all sorts of reason to justify it but in reality it's an old wives tale at best that the pump works harder...that's just dumb. Urban legends and such. Not running it dry (repeatedly) is sage advice but any other reason is made up bull.

[Petrol Head]

4 cars and a combined 450,000 miles of driving since 1997 here. I’ve always let my tank go till the low fuel light comes on.

Never once have I had a fuel pump, sending unit, or filter issue.

[Number 3]

the point in the tank where the fuel is taken from the is at the bottom of the thank. Otherwise you would have gallons of unusable fuel. So there is no more likelihood of picking up debris with an empty tank than a full one.

[Rock-It Man]

I can't imagine letting the fuel go below 1/4 tank for no other reason than peace of mind.

[Petrol Head]

Originally Posted by Number 3

the point in the tank where the fuel is taken from the is at the bottom of the thank. Otherwise you would have gallons of unusable fuel. So there is no more likelihood of picking up debris with an empty tank than a full one.

Good point. If it was eleveated in any way there'd be gas below the pump from the factory the day it rolled off the line after 10 years and a couple hundred thousand miles.