The Influence of an Oil Recycler on Lubricating Oil Quality with Oil Age for a Bus Using in Service Testing

A method of cleaning lubricating oil on line was investigated using a fine bypass particulate filter followed by an infra red heater, to remove water and light diesel fractions in the oil. Two bypass filter sizes of 6 and 1 micron were investigated, both filter sizes were effective but the one micron filter had the greatest benefit. This was tested on two nominally identical Euro 2 emissions compliance single decker buses, fitted with Cummins 6 cylinder 8.3 litre turbocharged intercooled engines. These vehicles had oil deterioration and emissions characteristics that were significantly different, in spite of their similar age and total mileage. Comparison was made with the oil quality on the same vehicles and engines with and without the on-line recycler. Oil samples were analysed about every 2000 miles. All tests started with an oil drain and fresh lubricating oil. The two buses were tested in a different sequence, one with the recycler fitted and then removed later in the test with no oil change and one with no recycler fitted at first and then fitted after an oil change. The bus with the recycler fitted and no oil change was also the one with the finer bypass filter. The test mileages were 28,000 miles for the bus that had the recycler tested starting from clean oil with the recycler and 48,000 miles for the bus that had the recycler fitted after 29,000 miles but no oil change. The amount of fresh oil top up was monitored and the results corrected for this dilution effect. The results showed that the on line oil recycler cleaning system reduced the rate of fall of the TBN and rate of increase of the TAN by 50% and 86% respectively for the two engines. The higher result was for the engine that had clean oil fitted for each of the tests with and without the recycler. There was a 50% reduction in the soot in oil by infra-red for both engines. The reduction in the rate of carbon accumulation in the oil was 68% for the engine with clean oil at the start of the test with and without the recycler and 36% for the other. The engines had very low fuel dilution and this was too low to detect an influence of the recycler on fuel dilution. There was also a reduction in the wear metals, for iron this was 38% and 85%, with the higher figure for the finer bypass filter. There was a small improvement of the fuel economy of about 3% if fresh oil was used when the recycler was fitted and 2% when the recycler was fitted without changing the oil. The lubricating oil consumption was reduced by 40% starting from fresh oil in each test and 60% when the recycler was fitted after 29,000 miles with no oil change.