A novel planar epsilon-near-zero (enz) tunnel sensor is designed using the surface integrated waveguide (siw) technology for detection of contamination in various petrochemicals. the proposed structure is about 275 and 1.8 times more compact than a conventional waveguide and a siw cavity sensor, respectively. in addition, the sample volume required to detect the contamination is as small as a drop having only 3 μl which is placed in the especially designed sample holder. the contamination is detected in real time in terms of the volumetric percentage by measuring the change in the dielectric properties of the reference and the adulterated samples. the method is based on the perturbation technique in which the tunneling electric field gets perturbed by the sample inclusion. the proposed sensor exhibits better sensitivity than the conventional waveguide sensors due to the presence of intense and nearly constant magnitude of the squeezed electric field inside the designed tunnel sensor, which is another advantage of the developed enz sensor for accurate measurement of petrochemicals. various types of adulterated petrochemicals are tested using this enz sensor, and the results are found to be in good agreement with the theoretical values. the developed sensor easily detects even less than 2% water contamination in petrol by producing large shift in the tunneling frequency, e.g. 800 khz shift in case of 2% adulteration is recorded, which is a quite challenging task presently being faced with the petrochemical industries. although this enz sensor is designed for petrochemical industries, it can be equally usable in pharmaceutical and dairy industries to detect the regular contamination.