240 Fuel Economy Gauge

[v8volvo]

Possible? Yes.

Will it tell you any useful information? No.

Those gauges are operated by manifold vacuum, so unlike on a gasser where the gauge's reading would correspond to engine load, on a diesel it would just read zero all the time. Not very helpful.

It might serve to inform you when it's time to change your air filter, if you let it get really plugged, but you'd already know that by the loss of power and the black cloud coming out the tailpipe...