A combination of various different fuel additive qualities and lubricant qualities were evaluated in a Mitsubishi direct injection gasoline engined vehicle over a standardized road test route using a controlled driving regime.
The evaluation was conducted using a matrix of a single base fuel combined with two inlet system detergent additives; one prepared using a synthetic fluidiser base and one a mineral oil fluidiser base. In addition a mineral and a synthetic based crank case lubricant were evaluated with clear base fuel only.
Engine inlet and exhaust valve deposits and combustion chamber deposits were measured along with regulated emissions, fuel economy and injector fouling.
Methods of measuring and evaluating deposit build up in the inlet and exhaust system and combustion chamber were constructed by developing existing Coordinating European Council (CEC) test methods and in house derived test methods and protocols.
The findings of this single car road trial are generally out of line with existing and established evidence of the behaviour of these products when tested in existing carburettor and port fuel injected engine technologies.
The deposit mass accumulation within the inlet system and on the inlet valves was not reduced by the inclusion of an inlet system detergent additive into the base fuel. Also data suggests that inlet valve, combustion chamber and exhaust valve deposits can be increased with the use of a gasoline detergent package, whereas the synthetic inlet system detergent additive did not contribute to adverse piston crown deposits.
The use of a synthetic lubricant did provide a reduction in deposit growth with reduced piston crown, bore ring reversal and piston bowl deposits, whereas combustion chamber squish face deposits were increased. Inlet valve deposits, although of similar weight to the synthetic fuel additive phase, were wet and fluid in nature and exhibited poor structural integrity.
This study has highlighted that the fuel and lubricant requirements of the Mitsubishi G-DI gasoline engine, with respect to control of inlet system, exhaust system and combustion chamber deposits are significantly different to those that are typically used in port fuel injection (PFI) and carburettor spark ignition engines.
Test methods are therefore required to evaluate fuel and lubricant performance in this emerging technology.