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This paper describes the observed impact of aniline octane booster and more specifically N-Methyl Aniline (NMA) on lubricating oil, following field issues encountered in vehicles in certain areas of the world where aniline based octane booster was assumed to be used. The observed field issue was heavy sludge formation, leading to engine malfunctions. The impact of NMA on lubricating oil could first be replicated using a modified version of the CEC L-109 oxidation bench test, with oil diluted with fuel and NMA at start of test. Significant kinematic viscosity (KV100) increase at the end of test was evidenced, especially as NMA content was increased in the oil. Total base number (TBN) evaluated at end of test also showed values above fresh oil (at or above 4.5 wt% NMA) that was consistent with observations from the field. The assessment of NMA impact was then scaled up using ACEA black sludge engine test.

This paper presents the results of part of the research activity carried out by the Politecnico di Torino and AVL List GmbH as part of the European Community InGAS Collaborative Project. The work was aimed at developing a combustion system for a mono-fuel turbocharged CNG engine, with specific focus on performance, fuel economy and emissions. A numerical and experimental analysis of the jet development and mixture formation in an optically accessible, single cylinder engine is presented in the paper. The experimental investigations were performed at the AVL laboratories by means of the planar laser-induced fluorescence technique, and revealed a cycle-to-cycle jet shape variability that depended, amongst others, on the injector characteristics and in-cylinder backpressure. Moreover, the mixing mechanism had to be optimized over a wide range of operating conditions, under both stratified lean and homogeneous stoichiometric modes.

The impact of N-Methyl Aniline (NMA) octane booster on lubricating oil has previously been studied and the main findings were reported in SAE paper 2016-01-2273. Increased sludge formation had been observed in modified ACEA black sludge testing when NMA was added to the fuel but there was very limited viscosity increase, which did not corroborate the trend evidenced on modified CEC L-109 oxidation testing where significant viscosity increase was noted when NMA was added to the oil and fuel mixture. Accordingly, modified black sludge tests have been run with and without NMA added to the oil sump at the beginning of the test to better match modified L-109 oxidation bench test conditions. Results showed the same trend in terms of viscosity increase between the modified L-109 oxidation bench test and black sludge test.