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This experimental work investigates the possibility of reducing the lubricating oil impact on diesel exhaust emissions, particularly concerning the particulate matter, by means of a three-stage experimentation on a Hydra Diesel research engine. The influence of the physical characteristics of the oil was evaluated in the first stage. The results showed that the use of low viscosity oils leads to a better mechanical efficiency and a lower specific fuel consumption than high viscosity oils in the examined viscosity range. Emission tests at a high constant load showed a higher Air Fuel Ratio (AFR) for low viscosity oils compared to high viscosity ones, due to a lesser fuel consumption. As CO, Particulate emissions and smoke are greatly affected by AFR at high load, a decrease of these emissions occurs moving towards low viscosity oils. The influence of the chemical characteristics of the oil was evaluated in the second stage.

A test procedure has been developed to investigate the effect of lubricating oils on the mechanical efficiency of car manual transmissions. The test is based on the measurement of the power dissipated in a closed mechanical loop, in order to allow for better precision compared to traditional output power measurements. The test apparatus fits two equal transmissions, operated by an electric motor. For the present investigation, two Fiat 126 car transmissions were used and a two load stage test procedure was adopted. Lubricating oils having different rheological and compositional characteristics have been tested. Test results discussed in terms of the effects of operating parameters and oil characteristics on transmission efficiency indicate significant advantages for oils containing synthetic basestocks and friction modifiers. Correlation of the test with friction measurements performed with a conventional tribometer is also considered.

The physical characteristics of lubricating oils can affect the mechanical efficiency of internal combustion engines and as a consequence the quantity of fuel consumed at constant power output; moreover they can influence the quantity of lubricating oil drawn through pistons and valves towards the combustion chamber. Exhaust emissions can be influenced both by fuel and oil consumption, so the physical characteristics of the oil can indirectly affect them. The purpose of this experimental work is to study the effect of the physical characteristics of lubricating oils on emissions, fuel economy and oil consumption in a light duty diesel engine. The study was carried out on a VM Turbotronic diesel engine characterized by low exhaust emission levels (1996 European limits for passenger car achieved without catalyst) and high specific power (37 kW/litre).

The present work, carried out within the framework of the JOULE-3 European joint project entitled “Fuel and lubricant formulations for high de-polluted engines”, investigates the effect of both the fuel and the lubricating oil quality on deposits, wear and exhaust emissions in the presence of a high EGR rate, with specific attention to the emission variation during aging. Two fuels (a current Italian typical fuel and a Swedish high quality fuel) and two lubricants (a traditional mineral oil SAE 15W-40/ACEA B2 and a full synthetic SAE 0W-40/ACEA B3) were used to carry out six tests, each one characterized by 126-hour duration at different running conditions, on a VM Turbotronic Diesel engine. The engine evaluation pointed out an interaction between oil and fuel: if the high quality fuel (nearly zero S) is used, a low level of cylinder bore polishing and top ring wear, weakly affected by the oil quality, occurs.