Running out of gas...

[C_Dave45]

Here's a curious question. How accurate are today's fuel gauges?
When the computer says you have a range of "67 kms" to empty...how accurate is this?
It's been almost 30 years since I've run out of gas. Back then, every analog fuel gauge was different. Some ran out before the needle barely touched red, others went well past empty and you could still be running on fumes.

I keep wanting to test my vehicle's computer to see how accurate it really is.
Anyone have any experience?

[sr20s14zenki]

Our 2004 duramax will go well beyond the fuel light haha. Usually when the fuel light comes on it'll say like 50k and I've. Gone more on the gas light. Couldn't find a diesel station that night haha.

[Graham_A_M]

Largely dependant on the vehicle. For the most part the gauges I've used were quite accurate, mind you I've never ever run out of gas so that whole argument as go just how much is left is kind of a moot point... but with my current bike, gas gauge is way off (common knowledge with these bikes) so I've modified it (splicing in resistors) so it's accurate, verified by how much the gauge is reading in terms of the amount of gas needed to fill it back up to full (in relation to how much they tank holds)

[Rat Fink]

.

[Mitsu3000gt]

In my experience they've been pretty accurate provided your driving is very constant (eg. highway sustained speed). Otherwise they are pretty inaccurate (eg. you might see a 30km drop in estimated range after only driving 5 or 10 km). If you look up how much fuel you have left when the empty light goes on in the manual, you can make a better estimate yourself. Also if you fill up at the same point each time (eg. as soon as the light comes on) and you notice you are always putting in about 50L of gas at that point, and you have a 60L tank, it becomes pretty easy to estimate your "reserve" range. That's what I've always done anyway. The gauges themselves I have found to be very accurate in the vehicles I've owned, if anything a bit on the conservative side.

I've never ran out of gas though so I don't have experience with that sepcifically. It's generally not great to run your car down to 'fumes', where the fuel pump might be sucking air when you corner, or where there might be a higher concentration of contaminants in the gas. Lots of people do anyway though and you never really hear of many issues.

[know1edge]

Those numbers are padded I think, I've frequently gone 1-5 kms when it says 0kms

[Aleks]

On our Honda Odyssey, km to empty is very accurate. With 30kms left to empty there's around 3-4L left in the tank.

With the Tundra however, the fuel light comes on with "30km" remaining, but at that point there's still 20L left in the tank and truck can go for well over 100km more.

[The_Penguin]

I miss that feature. One of the few things about my CTS that pisses me off, is when the DTE gets below a certain level (50Km I think) it displays "low" instead of the actual distance to empty.

[C_Dave45]

Lol....so, no one knows? Just like 30 years ago?
No starving university students who've actually ran out of gas with a computerized fuel gauge?
Rat Fink's post seems to be the most helpful.
One of these days I'm gonna put it to the test. Wife gives me shit if I go below "100 km's to empty".

[AndyL]

Throw a Jerry can in the back and drive till she pukes...

My ram 0km left - had about 20 more in her... The current gmc - under 19k left I'm fucked (seriously when dte switches from 19km to empty and flicks over to just low fuel - she's already dry)

[C_Dave45]

Originally posted by know1edge
Those numbers are padded I think, I've frequently gone 1-5 kms when it says 0kms

Interesting!! (Missed this as I was typing previous post)

[CompletelyNumb]

I've ran my ecoboost down to "5km to empty" before reaching the station. So at least it wasn't over estimating haha

[rx7boi]

Slightly off topic...isn't it risky/dangerous to a car to drive it until it runs out of gas completely?

I've wanted to test how many more km I can go before it's empty, but I don't wanna end up stuck on the side of the road

[killramos]

The "100km to empty" (generally) does not account for fuel reserve. So in that sense none of them are accurate. For example I'm pretty sure my FJ cruiser has 17L of fuel remaining below 0 or something ridiculous.

But in reality they are accurate, just know there is a fuel reserve below that number. Its pretty simple math, x L in tank ( pretty accurate) using xL/100km of fuel in the last 15 minutes ( very accurate in a fuel injected car) and gives you an estimate of how many km that fuel will last. If you start hypermiling the car while the warning is on your range will likely keep decreasing for a period of time before starting to drop again.

Its not hocus pocus, you just need to know how it works and what the car is actually telling you.

Also its shit for your fuel pump to run the gas to low.

Originally posted by rx7boi
Slightly off topic...isn't it risky to a car to drive it until it runs out of gas completely?

I've wanted to test how many more km I can go before it's empty, but I don't wanna end up stuck on the side of the road

Or pay for a new fuel pump like i mentioned.

[TYMSMNY]

Its calculated based on your average fuel consumption. If all of a sudden you take it on the highway, it'll start to recalculate and give you higher numbers.

Then again, I've hit 0 in a 4runner and had about a L left in the tank.

[pheoxs]

I've gone 5-10 passed 0 km to empty out of curiosity before I filled up. Though if you tried to accelerate hard or go up a hill you might have an issue.

I read somewhere a while back that north american cars always have a bit of extra grace so probably 1-2L left after it runs out, similar to how you could hit empty needle on the fuel gauge and still keep going. Whereas say JDM cars, you are basically out when you hit E. (From memory reading a long time ago, don't quote me on it though)

[C_Dave45]

Originally posted by killramos

Also its shit for your fuel pump to run the gas to low.

Or pay for a new fuel pump like i mentioned.

Very good point. Forgot about the fuel pump overheating if not immersed in fuel.
I guess it will remain just as how many licks to the Centre of a tootsie roll pop.

I used to run out of gas all the time back in high school. But that was in the days of carburetors and float bowls.

[project240]

We were heading to my aunt's house one day and wife had brought the car home low on diesel. Display in our Tdi said 20miles til empty, fortunately gas station is only about 10kms away. We got to the station and they were out of diesel, so didn't really have a choice, but to drive to next town with diesel, about 65km away. We were reading 15 miles til empty. I remember passing the highway sign saying 38km away shortly after the vehicle registered 0... Fortunately we made it, but was a very nervous ride...

[jacky4566]

Dave you wont do any harm with a test. The pump would need to be sucking on air for more than a few minutes to over heat.

Fill a Jerry can and go for a drive. When its empty turn it off, stop and refill. Done.

But to answer your question there is no standards for this kind of thing. I think the SAE has some recommendations but nothing official beyond (must show full, half, and empty)

[AndyL]

I'd worry more about needing to change a fuel filter - than a one time run out of fuel stress test on the fuel pump... By the time you're in that last 100km you're not effectively cooling an in tank pump anyway - unless your fuel tank is TINY...

But I'd never run a modern diesel out of fuel... That's a whole different kettle of fish