A silica suspended-core microstructured optical fiber sensor for detection of liquids, operating at 1550 nm, is analyzed. The sensing principle is based on the evanescent wave overlap into a tested analyte, which is filled via capillary forces into the cladding holes. Validations for analytes in the refractive index range of 1.35-1.43 are carried out with liquid-analyte-filling-length limits being studied both theoretically and experimentally. We prove, for the first time to our knowledge, that an extreme sensitivity of 342.86 dB/RIU and resolution of 4.4×10-5 can be achieved. This sensor represents a high-quality alternative for applications requiring a facile, low-cost solution.