Fuel guage calibration: how many gallons before tank is dry?
#1
Pro
Thread Starter
Fuel guage calibration: how many gallons before tank is dry?
I just know that someone has driven one of these C5 dry--ran it out of gas. How many gallons did it take to completely fill dry tanks?
I have never fillled up my C5 and placed more than 15 gallons of gas into the two tanks. Even when my warning light was on.
I presently have only 1/8 tank left--and the DIC says that I have a range of 115 miles still. And my average MPG on that tank is 28.4MPG. If the tanks should hold 18 gallons--1/8 of the tank should be 2.25 gallons. And the DIC says that I have a range of 115miles--from just over 2 gallons?
And it seems that the second half of the gauge goes down faster than the first half of the gauge. Is there a built in "safety net" into how the gas gauge is calibrated--it is actually pessimistic between the half full and empty part of the gauge ?
I have never fillled up my C5 and placed more than 15 gallons of gas into the two tanks. Even when my warning light was on.
I presently have only 1/8 tank left--and the DIC says that I have a range of 115 miles still. And my average MPG on that tank is 28.4MPG. If the tanks should hold 18 gallons--1/8 of the tank should be 2.25 gallons. And the DIC says that I have a range of 115miles--from just over 2 gallons?
And it seems that the second half of the gauge goes down faster than the first half of the gauge. Is there a built in "safety net" into how the gas gauge is calibrated--it is actually pessimistic between the half full and empty part of the gauge ?
Last edited by phoneman91; 08-30-2015 at 08:06 PM.
#2
Pro
Thread Starter
I've NEVER let my tank get below 1/8. Definitely a bad idea to run your tank dry. Reason: fuel pump at the bottom of the tank needs to stay immersed in gas to keep it from overheating. Just don't do it. Go by what your owner's manual says regarding tank capacity and don't even think about testing it.
What is the most gas pumped in a single fillup in your experience?
And I think that my tricky DIC is lying to me. 2.2 gallons left and still have a range of 115 miles?
Last edited by phoneman91; 08-30-2015 at 10:15 PM.
#4
Pro
Thread Starter
I appreciate everyone's response.
But--no one knows how the fuel gauge can show 1/8 tank left and the DIC shows 115 mile range left? With 28.4 MPG average on that tank. Is this range estimate accurate?
I suspect that there is a reserve of gas that is left in the tank --even though the gauge shows just 1/8 tank--approximately + - 2.2 gallons. It would seem that there is actually more than 2.2 gallons left. The amount of this reserve is apparently unknown to all of us .
And I was just wondering if anyone knew actually how much gallons it would take to fill both tanks from empty. 18 gallon tanks or 2001 MY 18.5 gallon tanks.
But--no one knows how the fuel gauge can show 1/8 tank left and the DIC shows 115 mile range left? With 28.4 MPG average on that tank. Is this range estimate accurate?
I suspect that there is a reserve of gas that is left in the tank --even though the gauge shows just 1/8 tank--approximately + - 2.2 gallons. It would seem that there is actually more than 2.2 gallons left. The amount of this reserve is apparently unknown to all of us .
And I was just wondering if anyone knew actually how much gallons it would take to fill both tanks from empty. 18 gallon tanks or 2001 MY 18.5 gallon tanks.
Last edited by phoneman91; 08-31-2015 at 09:37 PM.
#5
Safety Car
I ran my '98 dry years ago to check the gage and it took 19 gallons to fill. Once I ran out of gas and it took two gallons before it would start so now there are two emergency fold up jugs in the trunk in case it ever runs out again.
#6
Pro
Thread Starter
Thank you! I just knew that there had to be someone out there that ran these tanks dry.
Apparently there is a untallied "reserve" and the analog gauge doesnt reflect this--but the DIC range estimate mileage does. And this reserve is the reason that I can have a range of 115 miles left on an indicated "1/8 tank". The analog gauge is lying and is pessimistic.
The owner's manual only states:
"When the needle approaches the “E,” LOW FUEL
will appear on the display. At this time, you still have a
little fuel left, but you should get more soon."
Last edited by phoneman91; 08-31-2015 at 10:27 PM.
#7
Safety Car
I think that a dirty, restrictive fuel filter is responsible for more failed pumps than running the tank dry a few times. A restrictive filter places continuous extra stress on a running pump; my fuel pump is original with 116,000 miles on it but the fuel filter has been changed several times. After the gas gage let me run out I use the trip odometer and fill the tank around the 200 mile mark.
#9
Melting Slicks
Thank you! I just knew that there had to be someone out there that ran these tanks dry.
Apparently there is a untallied "reserve" and the analog gauge doesnt reflect this--but the DIC range estimate mileage does. And this reserve is the reason that I can have a range of 115 miles left on an indicated "1/8 tank". The analog gauge is lying and is pessimistic.
The owner's manual only states:
"When the needle approaches the “E,” LOW FUEL
will appear on the display. At this time, you still have a
little fuel left, but you should get more soon."
Apparently there is a untallied "reserve" and the analog gauge doesnt reflect this--but the DIC range estimate mileage does. And this reserve is the reason that I can have a range of 115 miles left on an indicated "1/8 tank". The analog gauge is lying and is pessimistic.
The owner's manual only states:
"When the needle approaches the “E,” LOW FUEL
will appear on the display. At this time, you still have a
little fuel left, but you should get more soon."
#10
Barry
#11
Melting Slicks
(The day I brought it home, it took 16+...I think the dealer was putting in a quart or two whenever it went out for a test drive.)
#12
Pro
Thread Starter
Thanks everyone for their responses to this thread. I usually do not run the tanks on my vehicles this low--but I like to get a sense of how true the gas gauge is on each vehicle and know how much reserve I have when the gas gauge shows the "E".
And I agree that keeping the tank full--leads to a longer life for the fuel pump. I have owned used vehicles that have had the fuel pump last twenty years/150k miles and more--that have had owners that didn't allow it to run with low fuel level.
The fuel pump is in the driver's side tank and the driver's side tank is the last to empty--and even when the gas gauge was on the last hash mark--the driver's side tank was just slightly less than half full--and would have kept the poor fuel pump covered in cooling fuel.
If the fuel gauge is calibrated on all C5s like mine--the driver would have to run it for at least 80 miles past the last hash mark--before running the poor C5 out of gas. Good to know.
Last edited by phoneman91; 09-02-2015 at 01:19 AM.
#13
Race Director
There's a little reserve on every car. I used to drive all my cars well below the "E", until I pushed it a little too far a few years ago and had a nice hike in hot weather.
#14
Safety Car
I've ran mine all the way to E a few times.
But the most I have ever managed to put in the tank is about 16.75 gallons. I think it's supposed to hold 18.5. The reserve fuel might not be accounted for. They obviously don't want the engine to stall out the second the needle hits empty.
I've also noticed the analog gas gauge doesn't appear to track linearly. When I fill up, it takes a long time to hit 3/4, but once it's down to 1/4, it seems to hit E more rapidly. Just my anecdotal observation.
But the most I have ever managed to put in the tank is about 16.75 gallons. I think it's supposed to hold 18.5. The reserve fuel might not be accounted for. They obviously don't want the engine to stall out the second the needle hits empty.
I've also noticed the analog gas gauge doesn't appear to track linearly. When I fill up, it takes a long time to hit 3/4, but once it's down to 1/4, it seems to hit E more rapidly. Just my anecdotal observation.
#15
Pro
Thread Starter
I have noticed that also. And the fact that the gauge goes quicker from one half to E than it does from full to one half. But if there is a hidden reverse of 4 gallons or so--it would explain this.
#16
Pro
Thread Starter
I agree that there is a reserve of some amount in all cars. Just a matter of finding out what the reserve is. Many car's owner's manuals will actually state the reserve. No so the C5 owner's manual.
#18
If you REALLY wanna know....Take the practical approach. If you are not afraid to let your tank run dry, take a 5 gallon fuel canister with you and then just drive until the car stops. Calculate the miles. Pull over, put that 5 gallons in the tank and be on your way.
If you are in no man's land where you don't know when you'll reach the next gas station, what I do is plan ahead and fill up before going through that area.
If you do this experiment, do post the results please. Would be good to know if that DIC was accurate.
If you are in no man's land where you don't know when you'll reach the next gas station, what I do is plan ahead and fill up before going through that area.
If you do this experiment, do post the results please. Would be good to know if that DIC was accurate.
#19
You can also use the trip odometer after filling it then see where it is when you refill it.
You can accurately calculate your mileage after monitoring a few tanks.
With that info you can figure out how far you can go based on the tank capacity.
You can accurately calculate your mileage after monitoring a few tanks.
With that info you can figure out how far you can go based on the tank capacity.
#20
Pro
Member Since: Feb 2014
Location: Kansas City Missouri
Posts: 697
Likes: 0
Received 6 Likes
on
4 Posts
My vette burns more fuel in town than on the highway so my mileage is from 24 mpg to 28 mpg per tank. It just depends on how much I do of either ... so I wouldn't count on the miles left to empty theory.