What is the formula for Miles To Empty?

[rafterscott]

Hey folks, so I'm trying to figure out exactly how Miles To Empty is calculated. It's my understanding that since the reserve tank isn't factored in (correct me if I'm wrong) what is the amount in the main tank multiplied against? MPG number perhaps from the last fill up?, MPG from say the last 200 miles driven or perhaps a few different factors?

Thanks as always, I haven't been able to dig up the answer yet.

[2001 SES]

I would personally think it's from the amount used (my dads trailblazer knows how many gallons of fuel it has used in its lifetime). I wish my 2001 had this because if I did my calculations right I'm getting 14.4 mpg In my duratec

[04 SEL]

It's a rough estimate. Computer knows how much gas is in the tank and it makes an educated guess on how many miles you have left by your current MPG.

[04 SEL]

Originally Posted by 2001 SES

I would personally think it's from the amount used (my dads trailblazer knows how many gallons of fuel it has used in its lifetime). I wish my 2001 had this because if I did my calculations right I'm getting 14.4 mpg In my duratec

That is terrible.

[Markcuda]

It's my understanding that since the reserve tank isn't factored in (correct me if I'm wrong) what is the amount in the main tank

Wow, didn't know we had two tanks on a Taurus

[behlinla]

Ford uses a typical reserve capacity of 10% (of the main gas tank, not a separate tank). In other words, when the tank level gets down to 10%, the display will show 0 miles to empty. The typical unusable capacity is maybe 3-5%. So when you get down to 5%, the fuel pickup is exposed, no more fuel can be pumped, and the engine stalls.

The other part of the equation is the running average fuel economy (RAFE), which is your average fuel economy over the past 500 miles. This is a separate parameter than the displayed average economy, and is non-user resettable. The only way of reseting is is perhaps by disconnecting the battery, otherwise you have to drive for 500 miles.

So the calculation is: (% tank level-10%) x tank capacity (gals) x RAFE (MPG)

In other words, if the driving style (and thus the typical fuel economy) suddenly changes, like if the car goes from being country car to a city car, the DTE calculation will be off for the first 500 miles or so.

You can view some of these parameters in ETM if you have a 2004+ with the digital display.