Hey there MCFF!
Quick question…I’ve owned 2 6th Gen MC. The first was an 02 LS and the second is an 02 DE. In the LS the low fuel indicator alerted at the yellow arrow. In the DE it alerts at the red arrow. (See attached photo) There is no way I’m that low on fuel when the gage is that high up. AND as we all know, when the low fuel indicator comes on in the info system simply states “lo” so there’s really no way to know how many miles or the distance left in the tank. In my LS the longest I ever HAD to go after the light came on was 17 miles with no issues. (I don’t like to push it, I’m not a run on fumes kinda girl) I’ve never “pushed” the DE to see just how far I can go.
Why such a huge variation between the 2 cars when it’s the same year/gen vehicle? Difference in model? Is this level preset or adjustable? Other than risking running out of fuel, any guesses on how many miles I’d have once it comes on in the DE with the gage being that high?
TIA

 

One thing to keep in mind is that these are not precision/calibrated gauges like you'd find in a test lab. TBH they're almost the polar opposite, especially with this era of GM (IE ultra cheap stepper motors). They're just for general reference. Ive a GM rental car where full was almost 2 full ticks past the F line, needle just floating out in space.

The only decent OEM gauges are some of the speedometers in police option cars (where it has a big label saying it's a calibrated gauge).

Id pay closer attention to the warning light as thats a mathematical formula based in part on the ohm reading from the fuel tank (so it only has one source of error - variability in the sender whereas the gauge gas 2 sources, the sender and gauge - which itself has a few variables).

There's a good reason for that. Part of it has to do with the variability Id mentioned before. Not every sending unit is made the same / mounted exactly at the same spot. So one car could actually run out at 2 ohms and another at 6 (just making up numbers for the point). Angle of the car / tank has an influence on that as well.

The other piece of that though is that miles left is based on average mpg not instant mpg (to dampen oscillation). If you've been driving flat roads for the last 3 hours and it trips the light with 50 miles to go, but at that same moment you came to the base of the Rocky mountains and were going to spend the next hour driving steeply up-hill (causing your mpg to plummet as you use much more throttle to get up the hill), then you're probably going to run out in 10 miles and be stranded on the side of the road with the screen saying you've got 40 miles still left. That leaves them with a liability (potentially a serious one if it happens in a dangerous spot) because their car said you had miles left.

The only point of that light is to signal you to get gas as soon as safe / feasible, and most anywhere in the country that occurs WAY before you would actually run out.

IMO, there's a better way to look at it: Absolute worst case you should go to the gas station immediately when that light comes on, regardless what the guage says. Ideally you'd even do it a little earlier. Two perspectives:

-Safety. If the light comes on and you ignore it knowing you've got 50-ish miles left and continue driving, what happens if you get into an emergency situation where you NEED to get away from danger and the car only has a few miles of gas left in the tank? I get that sounds a little doomsday prepper-ish, but medical emergencies do arise in everyone's lifetimes and an ambulance isn't always the best solution.

-Mechancial. The fuel pump is cooled by the fuel (which it also heats from the pumping process / running through the fuel rails of a 200 degree engine). The less fuel in the tank, the hotter the fuel and pump are going to run, and the greater chance for wear to it. This has been mitigated somewhat by the modern 'bucket' design where the the pump is always submerged until empty but the temperature of the fuel still gets hotter the less fuel is present in a return style fuel system, significantly so when you get to very small quantities of fuel being pumped back and forth again and again and again.


There's just no real upside to trying to see how low you can possibly push it unless you live WAY out in the boonies where it's quite a ways to the nearest gas station.

 

The reserve amount is supposed to be approximately 2 gallons. I have checked, ran it to the fuel light when I did my fuel pump and sucked out the remaining fuel. My 03 SS is almost exactly 10L. I’ve gone as far as 70 miles on the light (once in a desperate situation when I was younger and dumber lol) this was travelling at 70 mph no speed variances.
That being said, it’s a bad idea as the pump isn’t cooled properly plus sloshing creates air getting into the line creating a lean condition intermittently. Premature wear on the pump and to a small degree the motor will occur.

 

Hey there friends!
Thank you so much for the info on this. It all makes complete sense! As I mentioned, I’m not a “run on fumes” kinda driver but it is good to have this knowledge should a desperate need arise!

Blessings!!!