Adjusting MFA Fuel Consumption Readout

Mike Fishwick

Zorg Guru (II)
French Zeds
Joined
Sep 23, 2021
Points
109
Location
Daglan, France
Model of Z
2.8 Roadster
I have posted this procedure as an article, but thought it may be of interest here.

The MFA must be put into its Service Mode by turning the ignition switch to position 1, and then simultaneously pressing the 'Set Reset' and 'Clock' buttons. The display will now read '1.'

The MFA control push on the end of the indicator stalk can now be used to run through several functions, the display then reading from 1 to 5.

1 – 12/24 hour clock operation.

2 – Display Test – all segments operate.

3 – MPG Adjustment.

4 – Acoustic Warning Test (Low temperature buzzer sounds)

5 – Temperature Indication in degrees F or C.


Press the 'Set/Reset' button to enter the selected option – in options 1 and 5 the 'Clock' button can then be used to select the desired type of display.

The Fuel Consumption reading is selected by option 3, and after pressing the Set/Reset button the display will show its default setting of '1000.' The 'Clock' button can then be used to change the reading in an upward direction from 1000 to 1250, or from 1000 to 750.

The default setting is of course the number of metres in a kilometre, so a reduced reading will tell the MFA that a kilometre has been covered sooner – and that less fuel has therefore been used, and the indicated MPG will increase.

An increased setting will 'stretch' the distance, and the MFA will think that more fuel has been used to cover a kilometre, so reducing the MPG readout.

Accurate data is of course important, so always fill the tank to the brim, and keep a detailed record of the mileage covered and quantity of fuel used to brim the tank again. Calculate the amount of fuel used in gallons (4.5 litres per gallon).

From this data you can calculate the actual fuel consumption (miles divided by volume of petrol in gallons) and make a small adjustment to the MFA setting for the next tankful.

If possible always use the same petrol pump – I have found startling differences in MPG during identical driving conditions when using different pumps, as the permitted degree of accuracy is not as tight as one might assume.

Once you have reached an optimum setting you will be able to compare different fuels under identical driving conditions, which are a good comparison of both their thermal and anti-knock qualities. For example, when driving from the Dordogne to Salbris (S of Orleans) on our local supermarket's anonymous 98 octane, I usually get 35/36 mpg at a steady 80 mph. After filling up with Total Excellium 98 octane this improves to almost 40 mpg under the same conditions.

Using the much-vaunted Shell V-Power Nitro consumption increases to about 28 mpg, a figure which I have also found with the same fuel in the UK, and also with the corresponding BP fuel. The best fuel in the UK was always from Esso – their 98 octane Supreme being an equivalent to Excellium, and their 95 octane on a par with our local supermarket brew when driving at thespeed limit on motorways. Esso is about the only UK fuel which is not produced at Milford Haven, this difference showing that the octane rating is not an indication of a fuel's thermal content - the quality of the crude oil from which it is produced is more important. An overdose of ethanol is a cheap way of increasing a fuel's anti-knock (ie octane) rating, but as with any alcohol, ethanol is a poor fuel.

Having said this, I have not driven in the UK for several years, but regardless of fuel quality the best way to attain decent fuel consumption is a light right foot coupled with anticipation of road and traffic conditions.
 
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