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Petrol mileage display


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...and loses at the same time.. ;-)

I recently pulled up to a petrol station with only 1 mile left to go on the distance-to-empty having driven for nearly 20 miles looking for one that was open in the middle of the night. I had no idea whether it was accurate or not so it really was a nerve-wracking drive! One thing I did observe is that the countdown from around 20-30 miles or so was far quicker than the speed with which it drops in the rest of the scale.

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On 30/01/2018 at 11:45 AM, dansallis said:

I also reset all the 'resettable' options on my trip computer after re-fuelling. 

So I can only assume that it stores the data in the same way as the data for the gear change indicator.

If it does store all previous data, then I imagine it will use a 3 (approx) point moving average to determine the miles to zero. If it used fewer points the sample used would be inconclusive. If it used more the resultant value may not be representative. 

Below is a graph showing my average MPG for the last 7 fill ups and a 2, 3 and 4 point moving average used to predict my average MPG (and therefore miles to zero) for the 8th tank.

image.thumb.png.f33b15467dbde0c3d1bfe5337c76f701.png

As it happens, the predicted 41 MPG would give me a miles to zero value of 378 mi. When I filled up last it showed 381 mi. So, the 2 and 3 point moving average predictions are quite accurate, even despite the terribly unstable MPG data points!

what app or program do you use to get that graph

 

Jamie

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  • 2 weeks later...
On 28/01/2018 at 6:01 PM, Luke4efc said:

That'll be why then. Your MPG has dropped due to the short journeys and city driving rather than a constant speed on the motorway. The mileage remaining is calculated from the MPG you get and the amount of fuel left in the tank.

For example:
If you were getting 50MPG and had 2 gallons in the tank, you would have 100 miles to 0
If you are now getting 30MPG and still have 2 gallons in the tank you would have 60 miles to 0.

So Miles to 0 = MPG * Gallons in the tank.

I've done the calculations for you, and as the fiesta has a 42L tank (9.24 gallons), I've calculated your MPG figures off the mileage you were getting above.

You were therefore getting 48.7MPG (450 miles per tank) before
You're now getting 28.7MPG (265 Miles per tank).

That seems a very low MPG figure, try resetting the MPG figure by holding in the trip computer button for a few seconds and see what you get after that.

Hi Luke. Sorry for delayed response... Have been down with this horrible flu! 

So I reset the MPG figure. First day or so it was around 30-32mpg. Now it's between 27-29mpg...

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On 29/01/2018 at 8:54 AM, Tiexen said:

Be careful with doing that:


As the fuel level gets low the car will start picking up debris from the bottom of the tank. This can damage both the fuel filter and pump. 

Urban myth.  The pick up sits above the tank floor, there is no way it can suck up the last couple of litres of fuel.

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  • 2 years later...
On 1/28/2018 at 3:22 PM, RAIDER32 said:

The computer assumes an average based on your MPG,
Usually mine will say 250 Miles on a fill up if all I've done that month is short work & shopping trips,

When I've made a long trip to Cornwall and fill up down there it will say 380 Miles on a full tank,

That's due to the long cruise down getting 46mpg, compared to my shocking sub 25mpg heavy footed short urban trips.

My gas gauge shows correctly. It's my display. I had over half a tank, my fuel light came on saying I only had 49 miles to go. I filled it up, and it's saying I only have 160 miles to go. What do I go by, the display or the gas gauge? Please help..

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2 hours ago, Delia said:

My gas gauge shows correctly. It's my display. I had over half a tank, my fuel light came on saying I only had 49 miles to go. I filled it up, and it's saying I only have 160 miles to go. What do I go by, the display or the gas gauge? Please help..

Of cause they are all electronically controlled now, so either could have a fault, but i'd probably go off the fuel gauge its self.

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