Not sure if its me but the petrol gauge in my x-type seems awfully sensitive - been average 32MPG but gauge moves soooooooooo quickly is this usual or my imagination or driving skills? - and can anyone explain on how the gauge is calibrated.

did think i had a petrol leak but no smell or escape that I can see.

cheers buddies.

 

The gas gauge on all cars don't varry directly with how much fuel is in the tank because gas tanks in modern cars aren't perfect square boxes. With that being said I am curious as to if you are getting the gas mileage from the car computer or calculating it yourself. To check for the probability of a fuel leak, just fill your tank up all the way and note the odometer reading. Then drive for about a half a tank and fill it up to see how much gas you have used since the last odometer reading. If your calculated gas mileage (taken from odometer vs amount of fuel used) is less than 10mpg then you have a fuel leak. If you are around 20mpg then you are fine.

 

Jakey, please keep in mind that the tank in our cars is quazi split. What I mean by this is that there is a large hump in the center of the tank. So, the bottom half of the tank will cause the tank to be split into effectively 2 tanks. Hence why you have a transfer pump inside the tank. So, this can cause the fuel gauge to drop faster on the lower half of the tank. But, as the level drops on the one side, the transfer pump will move some of the fuel from the side with the higher level over. So, you will see the level gauge move up and down some. As long as you mileage is up like disguay said, don't worry about it.

 

When you put gas in your car do you only fill it part way, like 1/2 tank or less? If it is less than half the needle will move a lot quicker than if you fill the tank full for the reasons Thermo mentioned. I always fill my tank up and the needle moves a lot slower as I use up about half the fill. Once it gets to about the halfway point it goes much faster to empty. Nothing wrong.

One thing though. If you usually run it almost to empty and then only put in a couple gallons at a time you might notice the needle getting stuck and moving slowly or doing weird things. I know there were some posts about that a while ago. I can't remember why that was. I'm sure a quick search on here and you can find that. I know once I forgot to put gas in mine and it was down to about 20 miles to empty before I filled up and after it was full it took about 1/2 an hour for the needle to come all the way to fthe full setting. That was the only time that ever happend.

 

Guys, thanks very much for the explanation/s would seem all ok is world now i understand the mechanics of the petrol gauge. For the record on a run the trip computer tell me I get 390 to a full tank or around 32mpg = motorway work which in the scheme of things is pretty good going.

 

>around 32mpg

That's with an Imperial gallon, right? That's 5 quarts v.s. the US 4 quart gallon. So the 32 mpg you get compares to 25.6 for us. I regularly get ~22 mpg in mixed driving. So I'd assume that you drive slightly more highway miles than I do. But in general your mileage seems pretty consistent to what I get.

But is gas (i.e. petrol) still sold in gallon sizes in the UK or have you done a metric to imperial conversion?

It always bends my brain when I travel up to Canada and buy gas in litres and try to figure out: a) what I really paid for it, and b) what my gas mileage is while using it (grumble, ...Canadians fully implementing the metric system..., grumble, grumble...)
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Jaguar: Grace, Pace, and Space - Sir William Lyons

 

Hi Pab,

You are correct here in the UK we are 5 quarts or 4.4 litres in metric terms - agree really confusing. I do quite a lot of Highway or Motorway driving hence up at the 32mpg mark - trip B on the computer has never been reset so gives the overall mpg for the total mileage of the car and that's at about 26.4mpg

Hope this helps.