The biofuel ethanol, a viable and cost-effective gasoline substitute, is being blended at increasingly higher concentrations in gasoline, heightening the need to investigate its effects on current automotive engine lubricants in terms of fuel economy and engine durability. The friction at the piston ring/cylinder wall interface with a fully formulated gasoline engine lubricant contaminated with ethanol and water was investigated using a Plint TE77 reciprocating tribometer and reported in a previous paper by the authors. This research takes this one stage further by studying the friction in the same tribometer configuration when lubricated with the separated phases the same contaminated lubricant forms when left undisturbed, as would happen when a vehicle is parked or garaged. The lubricant mixture separated into two distinct phases, an oil phase and a water and ethanol based 'white sludge' phase, both phases characterised by FTIR spectroscopy and viscosity. Significant reductions in friction were obtained when the piston ring-cylinder wall interface was lubricated with the separated phases compared to the formulated reference lubricant. When lubricated with the separated oil phase, temperature was shown to be the dominant contributor to the frictional response. When lubricated with the separated sludge phase, ethanol independently contributed to the frictional response whilst the interactions between ethanol and temperature, water and temperature and water and speed were also important.

eprints@whiterose.ac.uk https://eprints.whiterose.ac.uk/ Reuse Unless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. Abstract: With tightening emission regulations, increased expected fuel economy, and longer drain intervals impacting on lubricant formulation, greater understanding of how oil degrades in an automotive engine is becoming ever more important. Equally significant is the effect that this degraded lubricant has on the tribological operation of the engine, particularly its overall internal friction and component wear. In a previous paper, four tests to degrade oil in a single cylinder engine were reported (Lee, P. M. et al. The degradation of lubricants in gasoline engines: development of a test procedure to evaluate engine oil degradation and its consequences for rheology. In 31st Leeds-Lyon Symposium). These tests were set up such that the lubricating oil was degraded in the ring pack before returning to the sump, where it was sampled and chemical and rheological analysis undertaken. This paper reports the extension of this work using the same Hydra engine and describes how oil has additionally been extracted from the rear of the top piston ring during engine operation. This extracted oil has then been subjected to similar analysis as the sump oil samples in the previous tests, along with additional analysis to look at the tribological properties of the oil using tribometers.The results clearly show significant differences in the rheological, tribological, and chemical properties of the fresh oil and used sump oil samples when compared with the top ring zone (TRZ) oil samples, particularly the effect of load on the levels of volatiles present in the TRZ samples and their effect on traction and friction coefficient values during tribological testing.

With increasing pressure on engine oil manufacturers to extend oil drain intervals and reduce fuel consumption, whilst changing the composition of fully formulated oils to meet new CEC, ILSAC and OEM specifications, there is ever increasing need to understand the effect of oil degradation on the operating conditions and tribological performance of engines. This poster presents mechanical changes made to a single cylinder research engine to enable the study of lubricant degradation, its transport and how this links to piston assembly tribology. A summary of the research undertaken using these changes and a sample of results obtained to date are also presented.