Low hours are useful information, but the history behind them matters.
First, establish what the advertised number means: hours since new, since major overhaul, or since installation. Those descriptions aren’t interchangeable.
Then look at how the engine was used. Was it flown regularly? Were there long periods in storage? Is preservation work recorded? Lycoming specifically warns that inactivity can allow internal corrosion to develop, even in an engine with relatively few operating hours.
An experienced engine inspector can use the records, filter findings, compression results and borescope examination to decide what further investigation is appropriate. A good compression result alone doesn’t establish the condition of every internal component.
Also check the current manufacturer’s overhaul guidance for the exact engine and the maintenance requirements applicable to that aircraft. Don’t assume that subtracting advertised hours from a generic TBO tells you how much useful service remains.
The Robin HR100 listing describes an engine installed in 2005 with approximately 380 hours since. Those are seller-reported details to verify against the engine records; they don’t establish its present condition.
Useful reading: Lycoming on evaluating low-time engines and Lycoming Service Instruction 1009BF.
What records or inspection findings would most influence your decision?