acbc, just wana ask....what do you use to flush the engine? Is it those flushing liquid that you see in shops? I would be extra careful using those stuff.
1. I dunno what they are made of, but i would assume some cleansing detergents. By pouring thiose thing inside the engine, it is like washing the vital engine oil away from the bearings, galleries, piston bore and skirt. so, when you flush it out, it seems that the internals are really dirty - just as you see from the flush and old oil mixture coming out from the sump.
2. so when u add fresh oil, those flush detergent will still be there a little and i assume it will contaminate the new oil and also, by that time, your engine internals would have NO OIL coatings. Just like you take a shiny shaft, coat it with oil. clean it with kerosene.
also will the flush damage the internal engine oil seals?
so far, i have never ever flushed my engine due to these reasons lingering in my mind. when i got my car used, my wallet took the pain and change the oil 2-3 times. sort of flushing the engine with engine oil.