Can you spot what's wrong?

Sep 16, 2026

You're in cruise, VFR, a few minutes from the airport. The engine sounds normal. You scan the engine cluster and see this. What's wrong?

AFuel imbalance, left/right

Good eye, the left tank does read a couple of gallons higher. That's ordinary for a 172 on BOTH, and a few gallons either way isn't something you'd act on in cruise. The gauge that's moving is on the lower row. Option D is the answer.

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BEGT probe failure

The red pointer on that gauge is the EGT reference bug, not the indication. The white needle is the one that reads, and it's sitting where it should be for cruise. Nothing on that gauge is telling you anything is wrong. The gauge that's moving is the one below it. Option D is the answer.

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CZero amps

Zero on that ammeter is the normal cruise reading. It shows current into or out of the battery, so a charged battery with the alternator carrying the load reads at the center. A dead alternator would swing it to the discharge side, and on this panel you'd see the low volts light too. Option D is the answer.

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DLow oil pressure

Correct. Oil pressure is slowly trending down toward the red line. If the temps are steady, the POH says it could be a faulty gauge. If temp starts to climb, the POH says pick a suitable landing spot and land as soon as possible.

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Pick an answer. You can try as many as you like.

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The explanation

D. Low oil pressure

Watch the trend

In the first frame every gauge looks normal. Over the clip, the oil pressure needle slowly trends down toward the red line. The lesson is the trend, not the snapshot.

What the POH says

If the oil pressure drops while the oil temperature stays steady, it could be a faulty gauge or relief valve. If the oil temperature starts to climb, pick a suitable landing spot and land as soon as possible. Either way, the engine won't tell you which one it was until it's too late, so plan to land at the nearest airport.

The gauges that look wrong but aren't

Fuel: the left tank reads a couple of gallons higher. That's ordinary for a 172 on BOTH.
EGT: the red pointer is the reference bug you set by hand. The white needle is the reading, and it's normal.
Ammeter: zero is the normal cruise reading. It shows current into or out of the battery, so a charged battery with the alternator carrying the load reads at the center. A dead alternator would swing it to the discharge side.