Evaluation of additives used in gasoline vehicles in China: fuel economy, regulated gaseous pollutants and volatile organic compounds based on both chassis dynamometer and on-road tests

Using gasoline additives is one of the economical approaches to achieving higher engine efficiency and lower pollutant emissions. However, a limited understanding of the actual effects of various additives is one obstacle to replacing outdated additive standards. In this study, the effects of 14 popular additives from the Chinese market on fuel consumption and carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx) emissions were evaluated based on the chassis dynamometer; then, one qualified additive was selected, and the on-road impacts on regulated gaseous and volatile organic compound (VOC) emissions were investigated using a portable emission measurement system. The results of the dynamometer tests showed that 9 of the 14 additives were beneficial in reducing CO emissions, with eight and seven beneficial for HC and NOx, respectively. Most of the test additives reduced the fuel consumption by 0.9–3.5%, while three additives had significant adverse effects. The on-road tests showed that the qualified additive could not only reduce on-road regulated gaseous emissions but also decrease most of VOC group, with decreases of 81.7% for aromatics, 79.4% for alkanes, 43.7% for halocarbons and 66.3% for alkenes. The vehicle-specific power (VSP) analysis showed that the test additive reductions in CO and HC emissions primarily occurred on highway roads because of the smoother vehicle operation. The results of this study indicated that quite a few additives might deteriorate the fuel consumption and tailpipe emissions, so the standards should be updated and market supervision should be further strengthened.