clearly I was wrong on the basis Simon reset his, and it reset to zero, so my understanding of it just changed :P

As for the driveability - get your radio code out, disconnect the battery and leave it for 30 minutes, then go back and start driving how you will continue to do so.

This will give you a chance to get your car to how you drive it.

I got my mondeo 6 months ago, first 3 tanks of fuel averaged 400 miles, reset the car, drove it as I do, I now get between 650 and 700 per tank.

James

does this method actually work?

How long does it take the car to learn, I mean is it after so many miles or is there (for example) say 5 slots in the memory that account for 5 journeys from engine start to engine off and when these fill up he car takes an average of the 5 and that's your driver settings?

or

does then car store say 5 slots (journeys) in memory which account for 5 different driver settings or driver/car input settings and then depending on the drivers input or driving conditions it sets the settings to the closest match from the 5 stored?

Is it a good idea if you buy a car to reset it so it can learn your driving style as in theory it would be set up to the previous drivers style?

clearly I was wrong on the basis Simon reset his, and it reset to zero, so my understanding of it just changed :P

Just thought I would see if the two are linked as they seem to be and on mine that is what it does. It does indeed reset to 0 along with the MPG readout. That does not mean to say what you said is wrong just noting my observations on my car at least.

As ever, I now have even more questions than answers.

Of course, I am still searching for the definitive proven RAFE definition, but now I really need to know if this battery-ECU reset idea to increase MPG really works. Because I have just been googling and once again there are different opinions: some say it works fullstop, some say it works but only temporarily because eventually it settles down to being pretty much what is was before the reset (suggesting that its ever changing and re-evaluating to the most recent driving) and some say its not possible on certain cars and some say its just bobbins. Personally, I remain open minded but if I am to belive it really does do something, I suspect it is just a temporary thing which then settles down to where it was before ... especially if what James says is true about RAFE (ie, its constantly re-evaluated over recent journeys and used in the calculation that effects the fuel efficiency).

So .....

1, RAFE: what is it really?

2, does disconnecting the battery REALLY make a long term difference to the fuel economy (anyone proved it over a long period of time)?

EDIT: a poll: http://fordfusionhybridforum.com/topic/7532-how-did-battery-hard-reset-affect-your-mpg/

(Ive just seen from google that the Aussies also have fuel economies displayed as L/100km's (as my RAFE does). And as they are also RHD, maybe my car is from a manufacture batch that could have gone to UK or Australiatown)

When you look at your OBC does it show MPG and ºC for the temperature or does it show L/100KM and ºF? Just curious.

As far as this learning process it is not something I have heard of before that has been proven, I have seen it said before, but I have had the battery off on my car when swapping to another battery albeit for less than half an hour but you would think long enough to reset the various ECU's, and I can't say hand on heart I have noticed any difference but I am happy to be proven wrong.

My OBC says MPG and Celcius (MPG because I have chosen Imperial measurement units in the Settings menu, and Celcius because you can choose). But the Diag menu always says L/100km for the RAFE.

I agree with you. May people suggest it works, many say not difference and as you say you havent actually noticed it making a difference for yourself, so yes I too am doubtful but willing to be proven wrong.

So your OBC is set to the same as mine yet it still shows the RAFE figure in L/100KM, how odd, I am wondering if this is a software issue on the PCM, the only thing I have done to mine is updated the PCM firmware to a newer version, it would be interesting to see if yours has the same software as mine or not. I don't suppose you have anything to read the software version of the firmware of your PCM do you?

I have tried changing the settings on mine again back to Metric and ºF and my RAFE still shows as MPG so that does not seem to affect the display unit.

As I say I am wondering of your firmware at some point has been updated to a different market one that would use L/100KM or as you say was originally a car that was intended too go to another RHD market but ended up staying here.

All I have is the TEST Diag menu. There are various ROM versions and wotnot, so I can read any of them to see if they match yours. Other than that, nothing else (I have no 'plug in' computers or anything - I am just an average Joe owner).

Note my model is an 08 plate TDCi. So possibly manufactured in 2007. Is yours a similar build date?

Mine is a 2006 registered car but MY03 I think. List the Rom details of yours and I will try and check mine when I can next.

Just thought I would see if the two are linked as they seem to be and on mine that is what it does. It does indeed reset to 0 along with the MPG readout. That does not mean to say what you said is wrong just noting my observations on my car at least.

Fair enough Simon, I would rather share information thats right and validated than not at all, so if it reflects to be the case that it is little more than active economy its good to know!

James

does this method actually work?

How long does it take the car to learn, I mean is it after so many miles or is there (for example) say 5 slots in the memory that account for 5 journeys from engine start to engine off and when these fill up he car takes an average of the 5 and that's your driver settings?

or

does then car store say 5 slots (journeys) in memory which account for 5 different driver settings or driver/car input settings and then depending on the drivers input or driving conditions it sets the settings to the closest match from the 5 stored?

Is it a good idea if you buy a car to reset it so it can learn your driving style as in theory it would be set up to the previous drivers style?

Absolutely it makes a difference. Cars willg enerally learn over the first 3 to 4 tanks and adjust accordingly.

The car remembers everything and bases the long term average, driver regardless. so for arguments sake if you do 4 tanks:

2 x heavy footed, averaging 20MPG and 2x Light footed averaging 40MPG, then it averages out at 30.

Likewise if you do 3 x 40MPG and 1 x 20MPG run, it will average 35MPG.

I can say from personal experience from resetting the CMAX and the Mondeo that it does work, MPG does improve as long as your driving stance improves. If I put my foot down, then the car does what I need it to do and then it starts to rebuilt itself afterwards. But given I bought the Mondeo about 7 months ago and reset it after 2, the last 5 months have all moved from an average of 400 Miles Per Tank to 600 - 700 Miles Per Tank on average. For this, I drive at 60MPH cruise control on the motorway 5 days a week (around 18 miles), I then do about 10 miles on country roads (A roads) averaging about 40 MPH and spend a lot of time on cruise control still. The other 2 miles per day are town driving. At the weekend, I tend to do about 20 - 40 miles in majority town driving circumstances. So I can safely say from personal experience that resetting the car makes ALL the difference.

As to the questions of what is RAFE, I think the earlier description is most accurate, and is basically average fuel economy since reset. With regards to the reason it displays in L/KM, this is likely due to the version of firmware on the cluster.

As to the questions of what is RAFE, I think the earlier description is most accurate, and is basically average fuel economy since reset.

Cheers. But can you explain why my RAFE reports it at being 42.6L/100km (about 6.7 MPG!)? Because it isnt. I get about 45 MPG everyday average driving (which is about the same as what my OBC says). So something just doesnt fit.

I dont disagree that changing your driving style changes your efficiency. I know it does. I did 2000 miles in August of which 1900 were probably fifth gear on motorways and my average went up to 57MPG. Tootling around town recently has dropped it down to 47MPG (which is roughly around where it is generally). And I have only topped up the tank once since being back from the trip. So it is clearly re-evaluating as things go along and not to do with fuel topups. But in any case NONE of the statistics in these facts have obvious relation to my RAFE showing 6.7MPG.

p.s When I top up my tank, it generally goes up to assume 525 miles on a full tank -to-empty which is about right what I get. When I topped ip from my 2200 trip (which finalised at about 54.5MPG) it estimated about 570 (I think, it may have been more) instead of 525 - of which clearly wont be the case and will be constantly adjusting as I get down to the 50miles-to-go alarm.

I think its purely the firmware that is reflecting the values you are seeing. I cant recall if you can set the value by pressing and holding reset on it when inside the trip computer. this may change it as you would want to be seen (MPG).

To be honest, I would take whats on their with a pinch of salt anyway. The whole instrument cluster self test is good, but without IDS to fully take the values apart and translate it, they arent the most accurate to read to you and I.

The fact your actual reading is about 4MPG more than your trip computer reports (albeit in L/100KM) then that seems to be reporting roughly what is correct. Bear in mind the tolerances in the OBC means that your never going to get 100% accurate reportings from there, which is why the OBC is almost always showing a different MPG to those who calculate it with the manual figures.

Honestly, I wouldnt worry about it too much, you might be able to update the firmware on the cluster and it may solve the issue, but would I bother for something I barely ever see? Not unless there was another issue I really needed fixing with the update.

In fact, I said earlier that I wished I had never asked because it isnt important and its just curiosity that's killing me. It was purely in the search of KNOWLEDGE, not need. And if I hadnt been snooping around and found out about the TEST diag menu, I would never have seen it anyway.

Lol fair enough and sorry if I seemed out of place as said things. Yeah it's true though, sadly Ford male things difficult to share information so most of what we find is a guess

No need for apologies, nothing taken as out of place. I like a discussion. (I REALLY like a discussion that ends in a definitive answer too. ;) )

(I am searching for help on another thread too if you want to add your thoughts to that too. :) )

Aye will have a look tomorrow if I can find it, unfortunately my phone battery is about to die lol so it won't be tonight :-P

Cheers. It's this: http://www.fordownersclub.com/forums/topic/19049-rear-bumper-removal-focus-2001-estate/#entry413264

Fair enough Simon, I would rather share information thats right and validated than not at all, so if it reflects to be the case that it is little more than active economy its good to know!

Absolutely it makes a difference. Cars willg enerally learn over the first 3 to 4 tanks and adjust accordingly.

The car remembers everything and bases the long term average, driver regardless. so for arguments sake if you do 4 tanks:

2 x heavy footed, averaging 20MPG and 2x Light footed averaging 40MPG, then it averages out at 30.

Likewise if you do 3 x 40MPG and 1 x 20MPG run, it will average 35MPG.

I can say from personal experience from resetting the CMAX and the Mondeo that it does work, MPG does improve as long as your driving stance improves. If I put my foot down, then the car does what I need it to do and then it starts to rebuilt itself afterwards. But given I bought the Mondeo about 7 months ago and reset it after 2, the last 5 months have all moved from an average of 400 Miles Per Tank to 600 - 700 Miles Per Tank on average. For this, I drive at 60MPH cruise control on the motorway 5 days a week (around 18 miles), I then do about 10 miles on country roads (A roads) averaging about 40 MPH and spend a lot of time on cruise control still. The other 2 miles per day are town driving. At the weekend, I tend to do about 20 - 40 miles in majority town driving circumstances. So I can safely say from personal experience that resetting the car makes ALL the difference.

As to the questions of what is RAFE, I think the earlier description is most accurate, and is basically average fuel economy since reset. With regards to the reason it displays in L/KM, this is likely due to the version of firmware on the cluster.

Thanks James.

I will try this out next time I do a full tank fill up. :)

Well I know this post is from 2014(!) but I think I have some useful information that may help settle it!

 

Background: 2012 plate pre facelift Mk3 Focus (UK), 135k ish miles on the clock. 

 

I’ve been into the test menu before on this car and my old mk6.5 (2007 facelift) Fiesta and wondered what RAFE was. Yesterday I don’t know why but had a fiddle when I got home from work, ended up in test mode and was again curious but this time actually decided to Google it again and found this thread. None the wiser really. Forgot about it again. 

 

When I got in my car to drive to work this morning my car suddenly said 50 miles to empty from not far off half a tank?! (yesterday said around 250ish), my average mpg had dropped from 51ish mpg to 5.3mpg, and my current MPG was showing around 5-7 when I was driving and something like 2.5gal/hour while stationary with engine running. Way off!

 

Either a massive coincidence somethings got confused and it will correct itself (unlikely) or I must have done something last night... 

 

So I re-entered the test menu, and the ‘AFE Bias’ menu caught my attention. Well, it turns out of you click ‘ok’, nothing seems to happen, but the up/down/left/right now change the values of this AFE Bias’, options ranging from 1 - 1999 (left/right: increase/decrease by 100, up/down increase/decrease by 1). Hit ok and it stores the value and you can continue to scroll up/down the test menu. 

 

So I had a play, and sure enough this setting gives an offset value to the MPG and miles to empty remaining. A low AFE made my distance remaining super low (50 mile range from just under half a tank), high AFE made my distance remaining ridiculously high (700 mile range from just under half a tank). 

 

I think I set the value to 1000 which seemed to put the values roughly to what it was originally. I record and reset my miles every time I fill up (always fill to the brim) and I’ve always found the MPG shown is close but about 2-5mpg above the real life figures I calculated by miles/fuel consumed. Always put it down to the pump not always clicking off at the same point or general calibration but now I should be able to fine tune it over the next few months by slightly adjusting the AFE. 

 

I recorded me scrolling through the menu, probably the most boring video ever but shows the figures changing. Note: In test mode the figures seem to show in KM not miles, so I also turned it off and on again to show it in miles when not in test mode too. 

 

Hope this helps somehow with your readings seeming to be inaccurate, OP! Try adjusting the AFE value and see if your readings make more sense. Even if it doesn’t help please report back so I can try and calibrate my findings with yours! (Wonder if you’ll ever even get to read this 6 years on!)

 

https://youtu.be/QGPmKGk6EFc 

The "RAFE" in test mode on your instrument cluster stands for "ROLLING" average fuel economy and is the average fuel economy since the car was driven off the production line.

I'm not sure if it can be reset, it's not something I've ever been bothered about