: Gas Tank Size?



Veritable
04-03-13, 03:30 PM
Had the V in-town as a daily driver for a bit over a week now, and had to fill it up.

The fuel gauge in the instrument cluster is divided into 10 increments, and when the needle got to the last bit before 0, the onboard computer started saying Low Range instead of showing any fuel range estimates. That's fine.

However, for this fill-up, I was only able to put 57.6L into the car, which is 15.22gal. This is the 3rd tank into the car, and it's been pretty consistent that getting to the last increment before 0 meant only being able to put in about 55L / 14.53gal. That's what I expected from my 5 years of BMW M3 ownership, except for one issue: the BMW had a 60L / 16gal tank.

My understanding is that the gen-2 Cadillac CTS has a 68L / 18gal tank? If the specs are right then is it correct for the last increment to represent a whopping 10L / 2.64gal of fuel left in the tank? That's almost 15% remaining....

How does the fuel gauge work for you guys?

elphil
04-03-13, 04:11 PM
I'm a quarter of a tank guy. I get to a quarter of a tank I fill it up. The design of the fuel monitor is overly cautious.

USAFRET
04-03-13, 04:49 PM
18 US gallons, GM has always had a pessimistic gas gauge, on all my vette's even with a LOW FUEL light on there was still at least 2 gallons in the tank.

stl_ls1gto
04-03-13, 04:53 PM
when you are getting 15mpg, they want it to have a 30mile reserve at least for you to get to a gas station....hence the 2 gallons or so when it says 0

cdog533
04-04-13, 01:47 PM
And don't forget, consumers hate accurate linear gas gauges as they give perceived 'bad' fuel economy.

That's why it stays pinned to 'F' for 100 miles, then takes about 75 miles to get to 1/2 tank, then falls to E in 40 miles.

Xaqtly
04-04-13, 01:59 PM
If the specs are right then is it correct for the last increment to represent a whopping 10L / 2.64gal of fuel left in the tank? That's almost 15% remaining....

Yep. in the CTS-V, on average, 2.64 gal of fuel represents maybe 40-50 miles to empty.


The design of the fuel monitor is overly cautious.

Yep.


18 US gallons, GM has always had a pessimistic gas gauge

Yep.


when you are getting 15mpg, they want it to have a 30mile reserve at least for you to get to a gas station

Yep.

The way this car drinks fuel, it's probably a good thing that you hit zero on the gauge with 2-3 gals left. The most I've ever put into mine was I think 16.1 gallons, and I was sweating bullets because I had been on empty for something like 15 miles already, so there is actually a huge safety margin built in.

hulksdaddy
04-04-13, 02:09 PM
Except, now that you know about the safety margin, it no longer applies.

Xaqtly
04-04-13, 02:28 PM
Yeah it's like Schrodinger's gas tank.

AussiePete
04-04-13, 04:45 PM
Yeah it's like Schrodinger's gas tank.

There's a dead cat in there...?

thefox1
04-04-13, 08:44 PM
On my G8 it said low fuel, then one time I saw very low fuel! Needless to say I ran out soon after ;)

ptrd
04-04-13, 10:16 PM
btw isn't it not good to run that low? doesn't it cause pre-mature wear on the fuel pump?

1997BlackETC
04-04-13, 10:36 PM
Yes, no good to run it down that low, it can make the fuel pump fail early because the gas cools the pump and when it's not submersed in enough gas it runs hotter.

Keep in mind too that the last gallon may not even get sucked up by the pump due to the design of the tank, so if you figure 2.5 gallons left is 30 or 40 miles in reality it may be only 20 miles or so. Best looking for gas soon after the low fuel indicator comes on or the best idea is to get gas around 1/4 or so as was said. That is the safest way of doing things.

HUGN*RDS
04-06-13, 11:31 AM
does somebody have a diagram of the fuel tank and internal pump assemblies? I know it would help me visualize the setup and I was just thinking about the low fuel warning too.

ptrd
04-07-13, 04:34 PM
I think i saw one in that "fuel pump issue where heavily modified cars weren't getting enough fuel" thread.