With the increasing use of ethanol blended motor fuels around the world, vehicle manufacturers as well as ethanol producers and distributors are interested in understanding ethanol's effects on materials corrosion. More specifically, General Motors continually evaluates fuel effects on fuel system materials and overall engine performance, and is studying the corrosive effects of chloride ions present in ethanol blended fuels, even at low part per million (ppm) levels. Chloride ions present in chemically polar motor fuels such as E85 are known to be one of the primary species involved in general pitting corrosion, galvanic corrosion, and stress corrosion cracking of automotive components. The authors conducted a 50K mile vehicle test program studying the performance and durability of two E85 Flex Fuel Vehicles (FFV) operating on E85, with specified ppm levels of chlorides.
The American Society for Testing Materials (ASTM) International has established fuel specifications that limit the chlorides concentrations in both denatured automotive ethanol (Ed100) and E85 motor fuels to 10 ppm and 1 ppm, respectively. The test vehicles for this study were a pair of 2008 E85 FFV Chevrolet Impalas, one operating on 2 ppm of chloride and the other a reference case without additional chloride added (ranging from 0.05-0.17 ppm). The authors evaluated and present data on fuel system component performance, vehicle operating performance metrics (tailpipe emissions, lubricant condition, engine control module (ECM) adaptive fuel controls, and on-board diagnostic (OBD) performance). End of test base engine material tear down inspection results are also included, which further examines the two vehicles run with different chloride concentrations.