I have a good buddy, still alive, who owns a Mooney. Fuel gauges were notoriously accurate (a rarity in GA aircraft it seems). The plane also has a fuel flow, but an old one that you reset when you fill up, but there's no way to add just partial and keep it accurate.
My buddy forgets to "reset" the fuel flow upon fueling. No problem, those fuel gauges are accurate. Plans a round trip across the Sierras with 16 showing on one side and 18 gallons on the other. Trip will take 10 gallons each way - - life is good, nice safe legal VFR reserves. The plan is to run the 18 gallon tank down to the low warning light point, then switch to the 16 gallon tank before crossing the mountains on the return flight. So far, so good.
About 15 from the Sierras on the homeward bound leg, the low fuel light comes on and the left "fuller" tank is selected. A few minutes later, now approaching the Sierra crest, the engine starts to stumble and stagger. "Buddy" is about 1000 feet above the peaks and the nearest airport South Lake Tahoe (TVL) is still miles away and on the other side of the ridge. Over enemy territory with only rocks, trees below, our friend switches to the known low tank and the engine comes to life . . . WHEW! Ah, for only about 30 seconds, then staggers and stops making power again. Oh $%^$. Losing altitude, engine running rough on either tank, Buddy declares an emergency to the tower at TVL (since closed), and is cleared to land.
Like me, my buddy flys gliders, so is conversant with energy management. His wife in the right seat says nothing as he continues to tell her what he's doing and why. With the still staggering engine adding just enough thrust to slow the desent, it looks like he may make the runway . . . all that glider time is coming in handy and he flys a high approach, only dropping gear, flaps and extending speed brakes on short final.
Exiting the plane, he half expects to see oil over the belly of the plane, he still can't believe the engine problem could be fuel exhaustion - - not with 16 gallons still in the left wing tank. But there's no oill mess and looking into the tanks is shocking - bone dry. Wife congratulates him on doing a great job . . but buddy is shocked, aghast that he has stupidly risked both their lives, so he tells wife that, no, he did not do a great job. He also made a promise to always, always visually check fuel.
I, of course, learned from my buddy's experience too, and always carefully check fuel.