Mig 29 fuel gauge "OPT" mode

[jeffy]

While flying the Mig I noticed a small lever on the top left corner of the fuel gauge what if you put it in opt will it like a fmc generate me an optimum altitude and engine rpm or whatever, so can a mig 29 expert tell me what the hell is it

[TerrorMango]

Not a MiG-29 expert in any way but according to the manual:

On the front panel of the ISTR4 indicator there is a switch "T-R" [9], to select information about remaining
fuel base on direct in-tank measurement or based on flow-measuring calculations of STR system; a switch
"TAC. – OPT." [2], change estimated distance indication: for max fuel conservative flight modes "OPT"
or for actual flight mode fuel consumption.
The ISTR4 scale provides fuel readings in hundreds of kilograms. The estimated distance in EN cockpit
in nautical miles

So in TAC, is hows you flight distance for regular flight "TAC" or for very conservative flight "OPT".

So when in OPT, the distance is greater than in TAC, but you'll have to adjust your way of flying to conserve fuel. I am unaware of which parameters actually constitutes this though in terms of speed, RPM etc.