[oldbeaver]

Dear UFO and Diesel_Dave,

Thank you guys for yr comments.

Well, it is clear to me that variability in air/fuel rate is too much for having a useful estimate of diesel mileage.

I have a Skoda Octavia diesel 2009 car with a onboard computer from Factory, and mpg variates a lot even in a flat surface with cruise control. A range from 10 to 100 is useless if we want to test mods and driving habits.

For making a measurement I use mean consumption with cruise control in a flat surface, starting recording at 70 km/h, not from stand still.

Any method will have, at least, the same variability of my Skoda.

The second method, using just GPS speed and aerodynamics, weight, and so for, must be calibrated several times comparing it with a full tank fuel consumption, to get any result close to reality. Even though, I expect a lot of variability o the road.

I tried to make a two flow sensors system, which "worked" when installed in the protoboard. I say "worked" but I cannot say worked well, because it didn´t. While soldering in a case for final versión it stopped to work and both flow meters begun to spill fuel and finally stop working. One main problem of very small fuel meters is dirty in fuel, that ends stucking the meters.

Oldbeaver