This is a tutorial on how to check and adjust the fuel burn in FSX/P3D (and FS9 I assume).

How to Determine Fuel Burn:
* This procedure should be similar for FS9, but in FS9 it is also important that tank configuration matches from FSE to your FS9 plane since the FS9 client deals with fuel a bit differently).

Make note of your fuel level (in gallons) at the start of a flight. Record this as value (A).
(If using the FSE client, be sure you record the fuel level just after starting the FSE client, using the figure inside the FSE client on your ‘my flights’ page as the start fuel)

Fly as you normally would to your desired altitude (it is best to use the altitude you will normally fly this plane at); once at altitude, set your speed to match the FSE cruise speed, record the FSE listed cruise speed as (D).

* If ‘full throttle’ is less than the FSE listed cruise speed, record the maximum speed your were able to obtain as (E), otherwise record the listed and obtained cruise speed as (E).

Finish your flight and land as your normally would, and make note of your fuel level (in the same manner as you did when the flight started) as soon as you land and FSE logs the flight, record this value as (B).

Go to your FSE log and get/record the time that the flight took in hours and minutes.

You will now need to convert the flight time to a decimal for use in the formulas…
Lets say your flight was 1:22 (one hour and twenty two minutes)
1 hour = 1, in fact the hours will always be the same
22 minutes gets converted like so: 22 / 60 = .36667 (I rounded this to 1.37)
next, add the hours and converted minutes together:
1 + .37 or 1.37 is what we will use for flight time in our calculations

Now subtract your end fuel (B) from your start fuel (A) to get the fuel burned on this trip:
Lets say you started with 500 gallons and ended with 200, so 500 – 200 means you burned 300 gallons of fuel in 1.37 hours.

Next divide the gallons burned by the flight time: 300 / 1.37 = 218.978 (we will call this 220 GPH)

Using this method we have determined that our plane burned about 220 GPH on this flight.

For this example we will also say that we could only obtain 230kts, but the listed speed in FSE is 250kts, this gives us one more figure to use in the calculations.
We divide 250 / 230 = .92
We will use this figure in our final calculation, just record it as the speed adjustment factor for now.

Setting Proper Fuel Burn:
To do this we will need to edit the ‘aircraft.cfg’ file for the plane we are working with. Locate that file, then open it in your favorite editor capable of working with text files. Next look for this line:
fuel_flow_scalar =

Lets say our says this: fuel_flow_scalar = 0.380
Record the fuel_scalar as Value (F).

Lets also say our plane should burn 200GPH @ 250kts, but as we determined above, it is actually burning 220GPH at 230kts, here is how we fix this…

Divide 200 / 220 = .909
Now Multiply this figure and our current fuel scalar: .909 * .38 = .345

If we were able to achieve 250kts we would be done, but since we were not, we should make one more adjustment…
Multiply the new scalar figure of .345 by the speed adjustment factor of .92 we recorded above:
.345 * .92 = .317

To apply this adjustment do this in your aircraft.cfg file; comment out the original line like so:
// fuel_flow_scalar = 0.380

Now directly under that line put a new line like so:
fuel_flow_scalar = 0.317

Save the file and that is it, you could now repeat the procedure to determine your new GPH in order to verify you have corrected the problem.