Low fuel light and potential reserve?

VelvetblackCT · November 18, 2016

Hello. Another newbie question - apologies if this is already covered somewhere.

Having had my (absolutely wonderful) CT200h for a couple of weeks, each time the fuel gets low enough to trigger the amber warning light next to the gauge, the 'cruising range' tells me I have only about 22 miles-worth of fuel left.

Is this an accurate estimate of how much remains? It seems alarmingly short-notice! (My Mini Cooper Diesel would alert me with nearly 100 miles to go). Am I being neurotic? Does anyone know how much is really left in the tank? I don't want to be blasé, and then find myself calling Lexus Assistance....

Any thoughts would be gratefully received!

Nick

floggit · November 18, 2016

Hi, only had mine for nearly a month now and light comes on around 25-26 for me but seems to drop quicker than miles covered so id be interested how much is actaully left in reserve. Read somewhere that the reserve is somewhat conservative.

steveledzep · November 18, 2016

Wouldn't consider letting the tank get that low personally, always fill up before reaching 1/4.

Bluesman · November 18, 2016

Hi Nick and welcome to the LOC. We are a friendly bunch so please don’t hold back asking questions big or small should you have any problems with your car. We always welcome ideas on how to overcome problems with our cars but as they are the finest cars in the universe they don’t go wrong that often.

We always love to see pictures of your cars so don't be shy.

Happy Lexus Motoring.

Mike. Bluesman.

VelvetblackCT · November 18, 2016

Ah - ok! I shall be much more careful in future. I was expecting to be told that the computer was being massively pessimistic and that I had many miles' leeway! I've been lulled into ignoring it by my previous Mini which warned me ridiculously early.

stormchaser · November 19, 2016

The tank capacity is 45 litres. It seems to keep 10 litres spare as zero comes up at around 35 litres used. Some people have gone beyond this and managed another 100 miles or so. It's well documented on the Prius forum about this but it's not really advised to let the CT get low on fuel. I've just filled up tonight as my range showed 32 miles. I only managed to put in 31 litres before it clicked off (£37). Still great on fuel and managing 55 mpg (calculated).

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Malc1 · November 19, 2016

sorry I'm hijacking here ............. so 14 litres left leaves you about 180 miles Reserve................. that's brilliant and nowt to worry about I guess when it hits orange ( does it then ? )

On my brilliant but now ancient Ls400 the gauge looks just about empty when it hits the orange and I know I've got about 100 miles left in the 85 litre tank ........ not having this fandangled modern technology that tells me how many ( dubious ) miles I might or might not have left of juice in the tank.

( I achieve about 30mpg at a steady 75/80 mph fully laden on the autoroutes of europe / Mway ( or should I say 70mph only ........... it's most efficient fuel consumption profile for me ) BUT drops to early 20's average usage )

Malc

VelvetblackCT · November 19, 2016

Thanks, everyone. That's what I was hoping for reassurance about, Paul - when I filled-up, it took just under 35 litres. I will try not to let it get so low, but at least I know that I'm not about to glide to a halt when the warning light comes on!

Zotto · November 19, 2016

The point to avoid to be without fuel in hybrid cars is that if this occurs, even not considering the risk to damage fuel pump, the driver insists moving in EV using traction Battery, till totally discharge, and with tractio battery discharged it's impossible to start the car: it needs a complex operation of recharging with an external charging machinery that is NOT common to find even in Lexus garages. So, need of towing and a long time to wait to fix the issue, and much money to spend.

This the reason why extimated miles in reserve are very prudential: on my GS with a 65 liters of tank the warning alert of low fuel appears with almost 10 liters and a indication of only 50 kms, while with my usual driving style I could do 160 more km. from light on (100 miles).

VelvetblackCT · November 19, 2016

That certainly explains why it is programmed to be so cautious - thank you. I'm just not going to get anywhere near the bottom of the tank from now on!

stormchaser · November 19, 2016

The point to avoid to be without fuel in hybrid cars is that if this occurs, even not considering the risk to damage fuel pump, the driver insists moving in EV using traction battery, till totally discharge, and with tractio battery discharged it's impossible to start the car: it needs a complex operation of recharging with an external charging machinery that is NOT common to find even in Lexus garages. So, need of towing and a long time to wait to fix the issue, and much money to spend.
This the reason why extimated miles in reserve are very prudential: on my GS with a 65 liters of tank the warning alert of low fuel appears with almost 10 liters and a indication of only 50 kms, while with my usual driving style I could do 160 more km. from light on (100 miles).

Exactly this.

This is how it was explained on the Prius forum. You can run out of fuel (if you wish at your risk as many have done)and run on EV until depleting your batteries but as explained you're completely goosed then and in need of assistance. I think I'll stick to 35 litres as you have done and I've got to before.

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Malc1 · November 20, 2016

.......technologically advanced modern cars might be, but oh don't they throw up worrying trends and stressful thoughts on what should otherwise be a pleasurable driving experience. Not knowing EXACTLY what's left in the tank, not worrying about EV capabilities and the technology needing super human efforts to resolve when a simple thing like a lack of petrol occurs ................ bring back simplicity of motoring and being given just enough information, not actually knowing that you're going to break down in 28 miles time and heaven forbid, having zero ECUs and glistening pretty lights on dashboards that forebode the death knell of what is a perfectly good car .............. bring back the " old " technology, maybe even a starting handle and oh, a bumper that actually does that, not a piece of re-enforced plastic that's going to cost a fortune to replace when it gets a little scratched and dented.

But then there's collision safety issues so maybe the newer the better ....... or maybe just very very careful driverless cars that I guess will never collide and eventually, when like in Delhi traffic, never actually move for fear of a scrape or two.

But I'm passionate about my V8 Ls400, petrol guzzling simple(r) technology that purrs along at very little expense apart from petrol .... in armchair comfort and the strength of a tank like structure to protect me.

Being old, am I allowed to say these things

Malc 1

Zotto · November 20, 2016

Being rather old compared to internet people, I am allowed too to be nostalgic too for some cars from previous century, but driving hybrid (or electric) is the future; after all the recommendation of filling fuel in empty tank could sound silly.

Usually I start to think for fuelling when reserve light is on, being sure that I can make much more km. without worrying.

ColinBarber · November 20, 2016

12 hours ago, stormchaser said:

Exactly this.

This is how it was explained on the Prius forum. You can run out of fuel (if you wish at your risk as many have done)and run on EV until depleting your batteries but as explained you're completely goosed then and in need of assistance. I think I'll stick to 35 litres as you have done and I've got to before.

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The vehicle won't deplete the batteries to an unsafe level in EV mode, there will always be enough reserve to start the engine unless you leave it for an extended period of time and the batteries naturally discharge.

rayaans · November 20, 2016

Usually you will have about 10L left when the low fuel light comes on.

However, I usually fill up around the 50 mile mark on the range - apparently low fuel isn't great for the fuel pump but not sure how true that is for modern cars

stormchaser · November 20, 2016

Exactly this.
This is how it was explained on the Prius forum. You can run out of fuel (if you wish at your risk as many have done)and run on EV until depleting your batteries but as explained you're completely goosed then and in need of assistance. I think I'll stick to 35 litres as you have done and I've got to before.

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The vehicle won't deplete the batteries to an unsafe level in EV mode, there will always be enough reserve to start the engine unless you leave it for an extended period of time and the batteries naturally discharge.

Yes very true. I've been down to 2 purple bars and it's fired up and recharged quickly. I should stop reading the US Prius forum and all the scare mongering of what happens haha. They certainly push there cars over the limits just for a few mpg more.

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Britprius · November 20, 2016

1 hour ago, stormchaser said:

The vehicle won't deplete the batteries to an unsafe level in EV mode, there will always be enough reserve to start the engine unless you leave it for an extended period of time and the batteries naturally discharge.

Yes very true. I've been down to 2 purple bars and it's fired up and recharged quickly. I should stop reading the US Prius forum and all the scare mongering of what happens haha. They certainly push there cars over the limits just for a few mpg more.

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The Battery is at about 50% state of charge with2 purple bars showing. However running on the Battery with no fuel will take the Battery to a level where the engine will no longer start. This can also happen if the car is left in neutral with the AC left running as the engine cannot start in neutral to keep the HV Battery charged. This has a knock on effect on the charge to the 12 volt Battery as this receives it's charge via a dc to dc inverter from the HV Battery The computer does not let the engine start when the HV battery is discharged to low to protect the Battery from cell reversal, and this is well documented on the Prius forums. The Lexus CT200H uses all of the Prius drive system.

The Battery self discharge rate is so slow that batteries that have been stood for 5 years have still maintained enough charge to register on the bar graph display, and start the car. Any bars showing on the display shows a charge level of above 40%, but not more than 80%. This is the range that the system is designed to work in to give long Battery life.

John.

VelvetblackCT · November 20, 2016

Thank you for all the technical info on this. My concern was about safe, real-world range, and the caution / conservatism of the on-board calculation. I shall try not to drop below an indicated cruising range of about 50 miles.

Nick

Zotto · November 21, 2016

Nick, about your concern, you can drive without worrying till indicated cruising range disappears ;-).

I see all the topic not a problem, before or after you will need to put fuel .

stormchaser · November 21, 2016

The vehicle won't deplete the batteries to an unsafe level in EV mode, there will always be enough reserve to start the engine unless you leave it for an extended period of time and the batteries naturally discharge.

Yes very true. I've been down to 2 purple bars and it's fired up and recharged quickly. I should stop reading the US Prius forum and all the scare mongering of what happens haha. They certainly push there cars over the limits just for a few mpg more.

Sent from my iPhone using Tapatalk

The Battery is at about 50% state of charge with2 purple bars showing. However running on the Battery with no fuel will take the Battery to a level where the engine will no longer start. This can also happen if the car is left in neutral with the AC left running as the engine cannot start in neutral to keep the HV Battery charged. This has a knock on effect on the charge to the 12 volt Battery as this receives it's charge via a dc to dc inverter from the HV Battery The computer does not let the engine start when the HV battery is discharged to low to protect the Battery from cell reversal, and this is well documented on the Prius forums. The Lexus CT200H uses all of the Prius drive system.

The Battery self discharge rate is so slow that batteries that have been stood for 5 years have still maintained enough charge to register on the bar graph display, and start the car. Any bars showing on the display shows a charge level of above 40%, but not more than 80%. This is the range that the system is designed to work in to give long Battery life.

John.

Thanks John for explaining this in detail. I'm still learning about this as I go along.

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