Impact of Gasoline Additives on Motorcycle Valve: Deposits and Emissions

In Mexico, the motorcycle fleet has surged by 191% since 2018 to 2025, driven by demand for affordable, fast transport. This study evaluated intake valve deposits in a 250 cc motorcycle (loaded tests) and a stationary engine (bench tests) over 60 hours, comparing gasolines with and without additives. Deposits were quantified by weighing with an analytical balance and characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Fourier-transform infrared spectroscopy (FTIR). Loaded tests (motorcycle, simulating city, highway, and mixed conditions) and unloaded tests (bench, continuous operation) revealed that gasoline without additives increased fuel consumption by ~68% in loaded tests and ~8% in unloaded tests, contributing to higher emissions and economic costs. Deposit accumulation was significantly higher in unloaded tests, with non-additive gasoline producing up to 304.8 mg of deposits compared to 122.2 mg with additives. SEM-EDS analysis showed that non-additive gasoline led to greater carbon (C) deposits, particularly on the valve body, while additives reduced carbon accumulation, maintaining valve sealing. FTIR confirmed organic deposits (C–H, C=O, C–O₂), and PO43-, SO42-, indicating thermal decomposition of gasoline and from 300 °C onward, a decarboxylation process begins to occur. Additives mitigate deposit formation, promoting cleaner combustion and improved engine efficiency.