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A methanol-fueled transit bus with a 1988-technology Detroit Diesel Corporation (DDC) 6V-92TA engine was chassis dynamometer tested using steady-state and transient cycles to determine exhaust emissions and fuel economy. With chemical-grade methanol (M100), the bus had lower particulate, NOx, and heavy aldehyde emissions than the comparable (though older) diesel bus; however, formaldehyde and organic emissions were higher. Two other approaches were tried: methanol with 15% added gasoline (M85) and an exhaust catalyst (with M100). Both reduced formaldehyde and organic emissions relative to M100 alone, but they both increased heavy aldehyde emissions. The exhaust catalyst also reduced particulate emissions.

A vehicle emissions round robin test program was conducted using a methanol-fueled vehicle operating on M85. Each of 16 participants conducted two to six Federal Test Procedure (FTP) emissions tests. All participants measured emission rates of hydrocarbon (HC), CO, NOx, methanol, formaldehyde, and acetaldehyde. One participant, designated as a reference lab, conducted emissions testing at the beginning, the end, and two intermediate times during the round robin. Results of the reference lab demonstrated that no significant drift in emissions levels occurred during the 2-year program. Relative lab-to-lab variability for FTP-composite emissions was lowest for NOx, with a coefficient of variation (C.V.) of 12%. CO variability was 16%, HC variabilities (by GC and bench FID) were 17 and 35%, respectively. Methanol, formaldehyde, and acetaldehyde were found to have variabilities of 34, 17, and 63%, respectively.