Originally Posted By: Jim Allen
Originally Posted By: Snagglefoot
Everyone should do this exercise. Use a one quart bottle to fill your new filter. Measure how much oil is left in the bottle. That way you know how much oil is left in the filter and
potentially how much dirty oil is in it. Some posters say they have one quart in their oil filter. While it depends on your filter I’m going to say most modern car filters hold less than a quart. Some less than a quarter of a quart. I’ll check mine next time.
Calling this "dirty oil" is a misnomer. Think about it.
1- That oil is as clean as your oil filter can make it. Additives depleted somewhat, of course.
2- New oil often has more contamination in it that the oil in your crankcase. It's a problem that Noria has discussed many times in their white papers and one that you can see when you have contamination analysis done to virgin oil. There are example here at BITOG. The makeup of the contamination between new oil and the used oil in your filter may be different, with what's in your filter likely having a concentration of small particles (smaller than the absolute rating of the filter) and the new oil having more big stuff.
3- Industry experts claim the smaller the contamination, the less harmful it is and as filter have grown more efficient, it's they are cleaning the oil better. I'm not 100 percent aboard on the "don't sweat the small stuff" but there is test data to support the argument. Of course the modern engines are running at somewhat closer tolerance in some areas and have things like variable cam timing devices that (if equipped) can be sensitive to smaller particles.
4- The final consideration is that the most modern engines, with good air filtration and low wear metal generation, are challenging the oil filter much less than the old "metal-monster" flat-tappet, rocker arm, timing chain metal shedding old school engine of the past. It might not have been a viable idea back in those days, but today, many cars need an oil change due to additive depletion long before the filter is an issue.
Anyway, if you think a little and factor everything in, you can make a logical decision as to whether your engine is a candidate for doubling up the FCI or not. Yeah, you can fall back on the no-brainer, "just do it" and while that solves the problem, any logical decision making to the process. Most likely... by a high percentage IMO... you are tossing a filter that is under 50% utilized.
Good post Jim Allen. Thank you.