Why 70m of range is a fuel warning
Discussion
I was talking to a friend about my Emira flagging up a warning on the dashboard for low fuel level/range which was a ridiculous 70 miles. He said it wasn't the range it was flagging up, it was probably the fact that with so little fuel in the tank the cooling of the fuel pump could be affected adversely, as most modern cars use the fuel itself to help cool the pump. Every day's a school day...
98elise said:
Beachbum said:
So basically when it says you have 425 miles of range, you really only have 350.
Why the hell doesnt it say that then ?!?!?!
Because you do have that range based in the fuel, its just best not to run it right down to nothing because of the pump.Why the hell doesnt it say that then ?!?!?!
Frimley111R said:
98elise said:
Beachbum said:
So basically when it says you have 425 miles of range, you really only have 350.
Why the hell doesnt it say that then ?!?!?!
Because you do have that range based in the fuel, its just best not to run it right down to nothing because of the pump.Why the hell doesnt it say that then ?!?!?!
Frimley111R said:
98elise said:
Beachbum said:
So basically when it says you have 425 miles of range, you really only have 350.
Why the hell doesnt it say that then ?!?!?!
Because you do have that range based in the fuel, its just best not to run it right down to nothing because of the pump.Why the hell doesnt it say that then ?!?!?!
Personally I just fill our cars up when they get to 1/4 tank. You never know if you might need to be somewhere in a hurry, or late at night.
Panamax said:
Depends where you live. Not so ridiculous in North America, for instance. What they're likely to find challenging is the limited range on a full tank, compared with other vehicles.
You will forgive me if I don't have much concern over whether an American will run out of fuel at present 
On a more serious note though, I rarely allow the fuel warning light to come on on any car. Many years ago I stupidly let the tank run too low and managed to block the entire fuel rail and 4 injectors on a Cavalier SRI as it sucked the detritus out of the fuel tank.
I tend to treat the activation of a low fuel warning as a mistake.
At around 60 miles left that comes on yup. Then about 40 miles later the petrol thing goes yellow. Then about 10 miles later it goes red and tells you you're almost out of fuel. Then 5 miles after that it stops telling you how many miles you have left just dotted lines. I think I ran it for another 10 miles before getting stopping for petrol. So basically it was pretty accurate - but I still think I coulda done another 5-10 miles or so without any problems. The problem becomes my girlfriend in the passenger seat saying things like 'isn't it about time an adult took this car to a petrol station?'. She's annoying like that.
Frimley111R said:
I was talking to a friend about my Emira flagging up a warning on the dashboard for low fuel level/range which was a ridiculous 70 miles. He said it wasn't the range it was flagging up, it was probably the fact that with so little fuel in the tank the cooling of the fuel pump could be affected adversely, as most modern cars use the fuel itself to help cool the pump. Every day's a school day...
So is there any basis of fact going on here, or just a mate said probably?jamesgareth said:
Sounds like the latter to me.
Hmmmmm. Grok seems to suggest I am wrong:"Yes, it is entirely true. Consistently running your vehicle with a very low fuel level can negatively affect the fuel pump, leading to premature failure, because the petrol (or diesel) acts as both a coolant and a lubricant for the pump.
Modern electric fuel pumps are almost always located inside the fuel tank, submerged in the fuel. Here is why low fuel is bad for them:
Overheating: The fuel surrounding the pump dissipates the heat it generates. When the fuel level is low, the pump is less submerged, causing it to run hotter."
Although the word 'consistently' is doing a lot of work in that first sentence.
jamesgareth said:
Hmmmmm. Grok seems to suggest I am wrong:
"Yes, it is entirely true. Consistently running your vehicle with a very low fuel level can negatively affect the fuel pump, leading to premature failure, because the petrol (or diesel) acts as both a coolant and a lubricant for the pump.
Modern electric fuel pumps are almost always located inside the fuel tank, submerged in the fuel. Here is why low fuel is bad for them:
Overheating: The fuel surrounding the pump dissipates the heat it generates. When the fuel level is low, the pump is less submerged, causing it to run hotter."
Although the word 'consistently' is doing a lot of work in that first sentence.
Petrol as a lubricant. I don't think so!"Yes, it is entirely true. Consistently running your vehicle with a very low fuel level can negatively affect the fuel pump, leading to premature failure, because the petrol (or diesel) acts as both a coolant and a lubricant for the pump.
Modern electric fuel pumps are almost always located inside the fuel tank, submerged in the fuel. Here is why low fuel is bad for them:
Overheating: The fuel surrounding the pump dissipates the heat it generates. When the fuel level is low, the pump is less submerged, causing it to run hotter."
Although the word 'consistently' is doing a lot of work in that first sentence.
BertBert said:
jamesgareth said:
Hmmmmm. Grok seems to suggest I am wrong:
"Yes, it is entirely true. Consistently running your vehicle with a very low fuel level can negatively affect the fuel pump, leading to premature failure, because the petrol (or diesel) acts as both a coolant and a lubricant for the pump.
Modern electric fuel pumps are almost always located inside the fuel tank, submerged in the fuel. Here is why low fuel is bad for them:
Overheating: The fuel surrounding the pump dissipates the heat it generates. When the fuel level is low, the pump is less submerged, causing it to run hotter."
Although the word 'consistently' is doing a lot of work in that first sentence.
Petrol as a lubricant. I don't think so!"Yes, it is entirely true. Consistently running your vehicle with a very low fuel level can negatively affect the fuel pump, leading to premature failure, because the petrol (or diesel) acts as both a coolant and a lubricant for the pump.
Modern electric fuel pumps are almost always located inside the fuel tank, submerged in the fuel. Here is why low fuel is bad for them:
Overheating: The fuel surrounding the pump dissipates the heat it generates. When the fuel level is low, the pump is less submerged, causing it to run hotter."
Although the word 'consistently' is doing a lot of work in that first sentence.
bcr5784 said:
James suggested it might be a coolant, not a lubricant. That seems quite plausible to me.
Well I shouldn't take any credit because it was chatgpt but yes the petrol in the tank acts as a coolant so the theory goes - not a lubricant. That would be an interesting piece of engineering to use petrol as a lubricant. In the cylinder block the oil behind the piston is doing the lubricating not the petrol above the piston. With the piston rings keeping the two liquids separate. At least says my 15 year old GCSE science brain.Frimley111R said:
I was talking to a friend about my Emira flagging up a warning on the dashboard for low fuel level/range which was a ridiculous 70 miles. He said it wasn't the range it was flagging up, it was probably the fact that with so little fuel in the tank the cooling of the fuel pump could be affected adversely, as most modern cars use the fuel itself to help cool the pump. Every day's a school day...
So the circulating fuel cools the pump but under 70 miles there isn’t enough fuel volume so the fuel starts to warm up? Maybe….dont some cars have fuel coolers now? It does seem a bit odd. Gassing Station | Emira | Top of Page | What's New | My Stuff