Had my 2018 1.5 182 Vignale since end of March 2021. Still love it. Great to look at and lovely to drive. But the shown MPG and range estimate have always bugged me.

The general fuel usage doesn't bother me, I don't use the car that regularly, couple of times a week? But I'm a bit OCD with figures! When I picked it up, MPG was showing 42.xx. Ever since I've had it, could not get it above 34.8! I've done around 13000 in 28 months. Most of that is visiting my step dad in Cornwall. Depending on traffic, either M25, M3, A303 & A30 (218 miles) or M25, M4, M5 & A30 (240 miles). I'm not a heavy right foot driver either, tend to cruise a lot, and use cruise control when I can.

So been there again this week and decided to do a non scientific test. Filled to the brim as I set off. Official Ford figures shows it has a 52 litre tank (11.438 gallons?).

Range showed 353....... arrived 218 miles and 3 hrs 45 mins later showing 282! For the first 90 mins the estimated range was increasing as I ate up the miles.  (😆) 

I did 444 miles in total on the trip and still showing 62 miles estimated range as I arrived home. The MPG is showing as 35.0.

But according to my match box maths, that's an MPG of 44.23? 506 miles divided by 11.438. So why can't the car show me those figures!?!?!

So, I am much happier knowing that on that sort of run I'm getting 44, just wish the car agreed with me! 

Fill it up again now and tell us the actual litres used and miles covered.  You've already said the range is unreliable, can't rely on that 62 miles remaining to be accurate.

32 minutes ago, TomsFocus said:

Fill it up again now and tell us the actual litres used and miles covered.  You've already said the range is unreliable, can't rely on that 62 miles remaining to be accurate.

Just put £30 in (which will most likely last me 2-3 weeks at least) and it’s now showing tank as half full with 290 mile range! 
 

So basically I have no idea now? How hard is it to get it accurate? 

Just now, jason56d said:

Just put £30 in (which will most likely last me 2-3 weeks at least) and it’s now showing tank as half full with 290 mile range! 
 

So basically I have no idea now? How hard is it to get it accurate? 

It'll never be accurate while you're only putting in small amounts at a time.  The float isn't perfectly accurate.  The tank isn't a perfect cube.

You need to brim it and drain it down to the red light a few times to get a more accurate indication on the dash.  If you also make note of the miles covered in between brimming and the litres taken to refill, you can calculate the MPG with more accuracy than the dash will ever show.

The key word in your first post is "estimate". The computer only acts as a rough guide.

As Tom says, "brim to brim" is the only way to get an accurate figure. And it has the added bonus of giving you some arithmetic practice, in line with the PMs targets!😀

 

 

If car fuel computers were 100% accurate and could predict the conditions of your future journey then I'd get one to give me this Saturdays lottery numbers  🤣

I don't use it frequently enough to do the brim to brim. About 75% of my miles have been trips to Cornwall and back. It replaced a getting unreliable 2010 Focus Zetec 1.6 TDCI with 125k on it (again mostly motorway miles) that was still telling me the mpg was 53 as I traded her in for this!

 

I appreciate it would never be completely accurate, but would hope it would be somewhere near! I will take it at around 40 mpg now as a closer figure than 34.something.

As I said, nothing major, just a minor annoyance to me in an otherwise great car.

You don't necessarily have to run it completely down to the red light before filling up. You can still get a reasonable calculation by brimming before you do your 218 or 240-mile trip then brimming again. Zero the trip counter before you start, note the exact mileage covered between brims and read the exact volume of fuel put in from the pump  It won't be quite as accurate as doing the calculation on a full tank but still a whole lot more accurate than the car's computer.

Running down to the red light was for the cars range calculation.  They seem to 'forget' where the bottom of the tank is if repeatedly filled from higher levels.

If you only want to manually calculate MPG that can be done from any level as long as it's brimmed each time.

Regarding the cars MPG reading, all you can do is reset it if it hasn't been reset for a while.

One thing to note about the range - if you generally do short, slow, low efficiency journeys, the car won't know when you're about to do a longer cruise...it will base your estimated range on the poor efficiency of your normal journeys.  That's why the range increased.  Likewise, when you refill after a cruise, it may estimate range higher in future, not expecting you to go back to lower efficiency journeys.It's a great bit of tech, but can't predict the future.

As long as you brim it once, then zero your trip, you can just keep adding top up fuel (keeping a record) until you next have an opportunity to brim it again You then have the advantage of doing your calculation over a longer period which gives a better idea of the underlying mpg.