Narrative:

Climbing out; I had a sudden loss of power. I immediately applied carburetor heat as I suspected possible carburetor ice. This temporarily made the engine run smoother. The loss of power was then more drastic; and when I removed carb heat the engine seemed to stop producing power altogether. I decided to turn back to ZZZ; and if I lost all power or was unable to make it I would land on the road or beach. In the meantime I extensively adjusted the mixture control and carb heat and whatever I could to attempt to restore power; but with no effect. I selected code XXXX in the transponder and began monitoring ZZZ tower. Since I was behind a mountain I did not immediately attempt contact. I heard tower reach out to me and I responded with my situation; [requested priority handling]; and advised I may land on the road. I continued inbound staying over the road while continuously evaluating potential off-airport ditching spots; but ultimately I was able to limp to ZZZ and make a successful landing on airport. My a&P (airframe and powerplant) has investigated and found that the fuel was contaminated with traces of water suspended in the fuel and small debris. No problems were discovered with the engine or fuel system itself after an extensive inspection. The plane was filled with mogas; regular automotive 87 octane fuel acquired from gas stations in town. The plane is stc'd (supplemental type certificate) to run mogas. There was a similar event with another avgas user just a few days prior; so it is suspected there may be a problem with the mogas supply in town at the moment. I plan to use avgas for the foreseeable future.

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Original NASA ASRS Text

Title: C-150 Pilot reported engine problems and returned to departure airport.

Narrative: Climbing out; I had a sudden loss of power. I immediately applied carburetor heat as I suspected possible carburetor ice. This temporarily made the engine run smoother. The loss of power was then more drastic; and when I removed carb heat the engine seemed to stop producing power altogether. I decided to turn back to ZZZ; and if I lost all power or was unable to make it I would land on the road or beach. In the meantime I extensively adjusted the mixture control and carb heat and whatever I could to attempt to restore power; but with no effect. I selected code XXXX in the transponder and began monitoring ZZZ Tower. Since I was behind a mountain I did not immediately attempt contact. I heard Tower reach out to me and I responded with my situation; [requested priority handling]; and advised I may land on the road. I continued inbound staying over the road while continuously evaluating potential off-airport ditching spots; but ultimately I was able to limp to ZZZ and make a successful landing on airport. My A&P (Airframe and Powerplant) has investigated and found that the fuel was contaminated with traces of water suspended in the fuel and small debris. No problems were discovered with the engine or fuel system itself after an extensive inspection. The plane was filled with mogas; regular automotive 87 octane fuel acquired from gas stations in town. The plane is STC'd (Supplemental Type Certificate) to run mogas. There was a similar event with another AvGas user just a few days prior; so it is suspected there may be a problem with the mogas supply in town at the moment. I plan to use AvGas for the foreseeable future.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.