Presumably the fuel tank was calibrated...

10778 Views 34 Replies 13 Participants Last post by KenC, Jun 21, 2014

KenC

Discussion Starter · May 6, 2014

... in liters I mean it seems obvious when the tank is 11.9 gallons or 45 liters, that it was made with liters in mind, since it was mfr'd in Japan. Why I ask is that I'm starting to suspect that the fuel gauge ¼ tank increments are 9 liters each, right? Split the tank into 5 parts of 9 liters. Of course, as I think in gallons, I had been calculating that the ¼ tank increments were a little over 2 gallons, which made the math a bit hard, so I've adjusted to thinking about the gauge increments in liters. I wonder if our Canadian and Brit owners were laughing at us Americans all this time?

Based upon that notion, then:
Full = 45 liters
¾ = 36 liters left or 9 liters used
½ = 27 liters left or 18 liters used
¼ = 18 liters left or 27 liters used
E = 9 liters left or 36 liters used

And the point is when the gauge hits Empty, that you have 9 liters or 2.4 gallons left. What's puzzling is the fuel range light. I'm wondering how that is calibrated. Is it 11 liters or 12 liters? I'm guessing 12, but I'll have to pay closer attention in the future.

I know many of you laugh about this fuel tank obsession, but I like to fill up as little as possible. I'm used to filling up with 1 or 2 gallons left in my old BMW's 16 gal tank, so it rankles if I've got 3+ gallons in the tank and 150 miles in range, when I fill up.

I mean look at the newest BMW i3 range-extender. It only has a 1.9 gallon tank! That's to eliminate range anxiety of EV-only. Our CTs signal for a refuel, 3+ gallons, which is 50% more than a full i3!

1 - 20 of 35 Posts

AspenCdn

· #2 · May 7, 2014

I think mine is at 'E' when there is 10l left. Several times now I have filled it and never put even 35l in. The low fuel light seems to appear with about 12l or sightly less left.
Based on that I would think the 1/4 tank increments are 8.75l each, but 9 is close enough. I think it is pretty safe to assume there is 160km or 100miles left to go once the low fuel light comes on. Set your trip meter when the light goes on and fill it when you dare.

The strange thing is that after fill up the range indicator assumes more than 35 litres can be used, but as you get closer to empty it doesn't factor in the last 10l of reserve.

Joe166

· #3 · May 7, 2014

I think the fuel gauge is inaccurate, biased toward not running out of gas. Anything more than that is more than I need (or want) to know.

Is it a sinister plan to make people think they are getting better mileage than they are? I doubt it since it seems to work in the wrong direction.

Is it some other devious plan?

How about using Occam's Razor? It is an inaccurate gauge that is not worth the trouble to fix.

darkphantom

· #4 · May 13, 2014

If it makes you feel any better, when the range hits "0 miles" - there is atleast 1-1.5gallons left

Clutchless

· #5 · May 13, 2014

Last week my car hit zero miles and when filled up took 9.6 gallons.

lostchild

· #6 · May 14, 2014

Clutchless said:
Last week my car hit zero miles and when filled up took 9.6 gallons.

Are you sure you JUST hit zero mile when you could put in 9.6 gallons? I don't think I could ever put in that much gas just hitting 0 mile. With 0 mile, I am closer to 8.5 gallons. I reset my Trip A meter every time I gas up now, so when it hits around 400 miles, I would do a refill. And usually it is already at 0 range left. At 400 miles, I usually fill up to 8.8 to 9 gallons.

Joe166

· #7 · May 14, 2014

Do you guys understand that there are too many variables for exactitude? Which makes these stentorian pronouncements useless?

Like the time of day, the weather (heat in the atmosphere), the shut off calibration of the pump, how far into the ground the tanks are (ground temperature), etc etc.

KenC

Discussion Starter · #8 · May 15, 2014

Joe166 said:
Do you guys understand that there are too many variables for exactitude? Which makes these stentorian pronouncements useless?

Like the time of day, the weather (heat in the atmosphere), the shut off calibration of the pump, how far into the ground the tanks are (ground temperature), etc etc.

Thanks Joe. Perhaps, the Lexus fuel meter is too inaccurate for us to try to understand what the Lexus engineers calibrated it to, but I do know my BMW fuel meter is incredibly precise. It doesn't matter the time of day, the weather, the shut off calibration, etc., etc., etc., the range estimate is exact.

My original post was to get some feedback on the experience of others. If there's any consistent bias, then we may be able to get a better understanding of what the gauge is SUPPOSED to be calibrated to. It seems ludicrous to me that I'm supposed to fill the tank, range equals zero, when I've only used about 9 gallons and have about 3 gallons or close to 150 miles in actual range left.

My BMW doesn't flash its fuel light until I have 50 miles in actual range left. The new BMW i3 only gives you 1.9 gallons for its range extender engine. If it were a Lexus, it'd tell you you were out of range even though the tank was full, with 1.9 gallons.

I honestly can't understand how a car could be built for fuel efficiency, be so inaccurate on fuel efficiency!

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bmoy88

· #9 · May 28, 2014

When my "Fill" light comes on I pump in approximately 35 liters.

chroma23

· #10 · May 28, 2014

for me, i drive no more than 50km when the fuel light comes up before i stop at the gas station. i never fill up more than 33 liters to full

KenC

Discussion Starter · #11 · May 29, 2014

Apparently, everyone's tank reading is different. Here are some results from above on when the fuel light comes on:

I guessed it would come on with 12 liters left, or 3.17 gallons.
AspenCdn believes it also indicates 12 liters or less left.
bmoy88 refills with approx 35 liters, meaning about 10 liters left.
chroma refills with less than 33 liters, meaning more than 12 liters left, but drives almost 50km more, or about 30 miles, about 2.5 liters more. So, he might have about 14.5 liters left.
My latest tank, the fuel light came on with 13 liters left.

Some others have refilled when hitting Range is Zero:

Clutchless refueled with 9.6 gallons, meaning 2.3 gallons left, or 9 liters.
Lostchild's estimate is about 8.5 gallons, meaning 3.4 gallons left, or 13 liters.
My latest tank, the range hits zero at 33 liters, or 12 liters left.

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Highvoltage23

· #12 · Jun 1, 2014

Ok, I have read enough of these full tank rants to finally post "IMO" rant myself.

Most fuel pumps are located in the tank. These pumps are motors that get hot. The gas in the tank keeps the pump cool. If to run the tank completely empty, or really low, the pump has no liquid to cool it down, so it gets hotter than usual. This is ok if you let it cool down slowly. The main cause of fuel pump failures is putting gas in an empty car that has been running for some longer period of time. (Putting cold fuel on a hot fuel pump. Ever put hot water on a frozen glass. It breaks. )

So what the heck does this have to do with the CT200? Everything. Lexus want to trick you into thinking the car will die if you don't get gas within the next 20 miles. In reality, this makes for a longer lasting fuel pump. The last 2 gallons in the tank are going to keep the pump cool. Some people don't know that this tank is 11.9 gal. So the fuel light is normal to them.

My dad was a mechanic for 25 years. He always told me to keep my tank above 1/4 of a tank.

So unless you only fill up when your fuel pump is cool or keep at least 2 gal in the tank at all time, plan on replacing a fuel pump on you baby.

BTW. Lexus fuel pump at dealer will be somewhere around $1000. DIY for about $200.

Take care of your baby. I do.

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bmoy88

· #13 · Jun 1, 2014

Here's a question - why, with today's technology, can't the car makers create a display that shows the amount of fuel left in the tank numerically instead of the outdated needle system?

midcow3

· #14 · Jun 1, 2014

Because Lawyers would have a field day.

bmoy88

· #15 · Jun 1, 2014

How so?

If the car shows 10 liters to go, I can decide to fill it then or to wait till it hits 5 - or 3.

KenC

Discussion Starter · #16 · Jun 1, 2014

bmoy88 said:
Here's a question - why, with today's technology, can't the car makers create a display that shows the amount of fuel left in the tank numerically instead of the outdated needle system?

My 2001 BMW 330xi has a spot-on fuel range meter. When it says "0", it means zero. When it says 4 miles left, you've got 4 miles left.

KenC

Discussion Starter · #17 · Jun 1, 2014

Highvoltage23 said:
Ok, I have read enough of these full tank rants to finally post "IMO" rant myself.

Most fuel pumps are located in the tank. These pumps are motors that get hot. The gas in the tank keeps the pump cool. If to run the tank completely empty, or really low, the pump has no liquid to cool it down, so it gets hotter than usual. This is ok if you let it cool down slowly. The main cause of fuel pump failures is putting gas in an empty car that has been running for some longer period of time. (Putting cold fuel on a hot fuel pump. Ever put hot water on a frozen glass. It breaks. )

So what the heck does this have to do with the CT200? Everything. Lexus want to trick you into thinking the car will die if you don't get gas within the next 20 miles. In reality, this makes for a longer lasting fuel pump. The last 2 gallons in the tank are going to keep the pump cool. Some people don't know that this tank is 11.9 gal. So the fuel light is normal to them.

My dad was a mechanic for 25 years. He always told me to keep my tank above 1/4 of a tank.

So unless you only fill up when your fuel pump is cool or keep at least 2 gal in the tank at all time, plan on replacing a fuel pump on you baby.

BTW. Lexus fuel pump at dealer will be somewhere around $1000. DIY for about $200.

Take care of your baby. I do.
Sent from AutoGuide.com Free App

Thanks for that. I wonder why you never read about keeping your fuel pump cool in the manual, or driving tips on the internet, instead you have to read it from helpful people?

Back to the fuel pump, what do people with the new BMW i3 range extender do, since they only get a 1.9 gallon fuel tank? They probably have some other way to keep that fuel pump cool, and if they do, why don't other car mfrs do something similar? Is it too much to ask, since they don't tell us why they do the things they do, like why does the fuel range light come on when there's about 3.5 gallons left? I'd love it if it came on with 2 gallons left, since that's exactly what my 2001 BMW does. 2 gallons and bingo, the light comes on.

CaspianM

· #18 · Jun 1, 2014

Without knowing all the info about the design & configuration of the fuel pump in CT200 all the talks are just speculations imo.

bsnguy

· #19 · Jun 2, 2014

bmoy88 said:
How so?

If the car shows 10 liters to go, I can decide to fill it then or to wait till it hits 5 - or 3.

Well, if it showed a number then any number odd people I this site would try to determine if it was accurate and create a thread about how it's not. Then someone would get the idea to start a class action lawsuit about it...

(Tongue implanted in cheek)

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darkphantom

· #20 · Jun 7, 2014

Just filled up today a bit after the tank hit 0 miles, filled up 8.8 gallons, which makes me believe that when you do see the 0 mile sign, you have ATLEAST 3 gallons left.

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