Lightwater wrote:

Fill up the tank then write down the data (I write on the back of the receipt), then reset the trip meter. You really need to reset if every tank-full as the data will get less & less meaningful.

What sort of MPG difference does using the Air Conditioning (cooling) make.

It seems to be at least 2 -3 MPG in my case, therefore I achieve my best MPG figures in the mild Spring and Autumn temperatures.
i.e. least engine warm-up and zero Ian cooling. FL2 XS SD4 Auto 2010 2012-2017 (21k - 91k miles) (MY2011)
FL2 Metropolis SD4 Auto 2014 2017- (16k - 76k+ miles) (MY2015)

Here in Canada, they are already selling "winter" gas and the MPG, in our case KPL, are generally worse. The combo of this type of gas, winter tires & the cold, gas consumption generally increases. Now I am still driving on my summer tires for likely another month or so.

On a few of our highways on the straight sections we have a section of 5 km so you can compare the car's odometer to the real milage. With standard sized tyres the car is a far bit under actual distance. If the tyres are worn it is even a greater reduction in distance.

If you have larger tyres your rolling distance is closer to actual distance. You also need to factor in old tyres as they have less tread & thus a shorter rolling diameter. The car is traveling a shorter distance than the computer think's it is.

I think you would need a rolling diameter of about 2.455 metres to match the real distance. If your tyres are worn with about 3.7mm reduction of tread that is about another additional 1% you have to reduce your milage by.

So worn tyres 235/60R18 by 3.7mm = 2.2984mm rolling diameter. So if the car says 40mpg, all you are actually achieving is 37.45mpg.

235/50R20 2.334m
235/60R19 2.327m
235/60R18 2.322m
255/60R18 2.395m
245/70R17 2.433m Procrastination, mankind's greatest labour saving device!

Acoustic insulation ARB TPMS 3xARB air compressors After cooler Air tank On-board OCD pressure air/water cleaning Additional 50L fuel Carpet in doors ABE 2x1kg Waeco 28L modified fridge Battery 4x26ah Solar 120w Victron MPPT 100/20 DC-DC 18amps 175amp jumper plug Awning 6x255/60R18

Last edited by Lightwater on 14th Oct 2019 10:10 am. Edited 1 time in total

IanMetro wrote:

What sort of MPG difference does using the Air Conditioning (cooling) make.

It seems to be at least 2 -3 MPG in my case, therefore I achieve my best MPG figures in the mild Spring and Autumn temperatures.
i.e. least engine warm-up and zero Ian cooling.

CED wrote:

Lightwater wrote:

Fill up the tank then write down the data (I write on the back of the receipt), then reset the trip meter. You really need to reset if every tank-full as the data will get less & less meaningful.

i have to agree, the figures that the computer come up with bear no relation to a careful monitoring of tank to tank usage. Making sure you put the same amount of fuel in every time , you will be disappointed with the real MPG figure.