Last year my 93 YJ 2.5L Failed miserabily, $600 later and no emmissions Sensors involved, it passed. A 4cylinder!!!!!. This morning I filled up with regular, put a half quart of denatured Alcohol (from the hardware store, $5.00) drove 25 miles and went to have it inspected. Between the test person and the mamager there was a discussion of why the emmission results were so low. I passed with flying colors, almost zero emmissions. The Alcohol burns hotter and burns more of the gasses.