Prior installing the bypass filter I noticed the M1 5W30 oil in my 2003 Toyota Echo turned dark brown very soon, and had to change it every 3k miles even though I did very few short trips. It seems Echo is very hard on oil. I do not understand why Toyota recommends >3k miles OCI.
Yesterday I change the first TP after 2k miles on the oil because the oil looked much darker than I expected even with a bypass filter. I put in a new TP, drained out 1 pint of used oil from the oil pan, and add 1 quart of fresh oil and 5 oz of Lube Control (LC) oil additive. It is surprising to see the color of oil returns to golden yellow resemble that of brand new oil after driving to work this morning, which allowed the bypass filter to clean the oil a bit. Either the old TP was so saturated with contaminants with only 2k miles of service that it could no longer filter properly, or the engine oil was running out anti-oxidant such that the engine oil became dark brown. For some reasons the Echo engine soils its oil in a relatively short period of driving. With the addition of LC (containing anti-oxidant) the oil hopefully might not look too bad after another 2k miles; otherwise, I would replace the TP at shorter interval like 15k miles. I think the TP, FF filter, and oil change intervals need to be tailored to an individual engine design.