  Citation: Rossegger, B.; Leis, A.; Vareka, M.; Engelmayer, M.; Wimmer, A. Lubricating Oil Consumption Measurement on Large Gas Engines. Lubricants 2022, 10, 40. https:// doi.org/10.3390/lubricants10030040 Received: 24 January 2022 Accepted: 3 March 2022 Published: 8 March 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). lubricants Article Lubricating Oil Consumption Measurement on Large Gas Engines Bernhard Rossegger 1, *, Albrecht Leis 2 , Martin Vareka 1,3 , Michael Engelmayer 1 and Andreas Wimmer 1,4 1 Large Engines Competence Center GmbH, 8010 Graz, Austria; martin.vareka@tugraz.at (M.V.); michael.engelmayer@lec.tugraz.at (M.E.); andreas.wimmer@lec.tugraz.at (A.W.) 2 JR AquaConSol GmbH, 8010 Graz, Austria; albrecht.leis@jr-aquaconsol.at 3 Institute of Organic Chemistry, Graz University of Technology, 8010 Graz, Austria 4 Institute of Combustion Engines and Thermodynamics, Graz University of Technology, 8010 Graz, Austria * Correspondence: bernhard.rossegger@lec.tugraz.at Abstract: Increasing the reliability of combustion engines while further reducing emissions and life cycle costs are the main drivers for optimizing lubricating oil consumption (LOC). However, in order to reduce the lube oil consumption of an engine, it is crucial to measure it accurately. Therefore, a LOC measurement device based on the use of the stable isotope deuterium has been developed. Previous publications have focused on the use of passenger car engines. This publication describes the first application of this newly developed method on a large gas engine. This is of particular interest as large-bore engines might show different oil consumption behavior, much higher LOC in gram per hour and the bigger oil reservoir need larger amounts of tracer. Additionally, a different type of fuel has an effect on oil consumption measurement as well, as presented in this paper. The results showed this method can be applied to large gas engines as well after conducting minor changes to the measurement setup. However, other than liquid fuels, the origin and isotopic composition of the natural gas has to be monitored. Ideally, gas from large storage is used for carrying out these measurements. Keywords: lubrication; oil consumption; tracer; deuterium; IR spectroscopy 1. Introduction As internal combustion engines operate at high speeds and loads, continuous lu- brication of the piston group is indispensable in order to prevent scuffing and provide optimized mechanical efficiency. Moreover, the tribological properties of the piston group— lubrication, wear, and friction—are omnipresent research topics in the field of combustion engines. However, as the combustion engine is an open system, with masses constantly en- tering and exiting the system boundaries, the lubricating oil itself is continuously consumed as well. Increasing reliability of combustion engines while further reducing emissions and life cycle cost are main drivers for optimizing the lubricating oil consumption (LOC). Above all, lowering the life cycle cost by extending the time between overhaul (TBO) would be a key benefit of a LOC reduction. Contaminants coming from the oil are considered to lead to poisoning of catalytic materials of the exhaust gas after-treatment system. Precious metal catalysts as used in catalytic oxidation catalysts to convert residual organic compounds and also as a part of selective catalytic reaction (SCR) and ammonia slip catalyst (ASC) systems to reduce nitrogen oxide emissions from large engines are very sensitive to poisoning by sulfur and phosphorus from the engine oil. Another highly important point is the influence of oil droplets on combustion anomalies, for example, as a preignition resulting knocking of an engine, described in [1]. Currently, these are the main drivers for reducing the oil consumption of an engine. However, further legislative limitations of carbon dioxide emissions of engines already operating on carbon-free fuels will address the oil consumption of an engine. Therefore, Lubricants 2022, 10, 40. https://doi.org/10.3390/lubricants10030040 https://www.mdpi.com/journal/lubricants