Originally Posted By: actionstan
... However I would like to start using a larger filter, so the oil stays clean looking longer. The oil turns dark very quickly, Its starting to stay cleaner longer with regular oil changes. I feel like a bigger filter would help with the cleaning process. (I understand color does not necessarily indicate bad oil.)
Welcome to the site!
You are correct in that color has no real indication of lube health; it will turn dark quickly, but that does not infer the lube is in bad shape whatsoever.
You are making an incorrect assumption that using a larger filter will result in cleaner oil. It will generally add some holding capacity, but since most filters have WAY more ability to hold particulate than the normal OCI would ever present, it's a moot point. Going larger is adding capacity you'll never use, especially when you don't use all of what available now, most likely.
There is debate in theory about which would present a greater advantage:
1) larger filter slightly slows fluid flow rate through media, thereby allowing a better capture ratio, increasing efficiency
2) smaller filter would actually load more quickly, thereby providing ever smaller holes to capture particulate, increasing efficiency
I have yet to ever see a true study done where the DOE is to prove/disprove the size option relative to overall beta performance over the life of the intended OCI. I'm an SAE member, and I've not see a study unique to that mantra in their catalog, and most filter studies are older, which would even make some question the relevance in regard to today's engines and lubes.
You can upsize if you want but you're not likely to see any statisitically signficant shift in wear or cleanliness rates.
What improvement you might be seeing in "color" shifts is due to frequent OCIs and not your filter choice. Soot (the main ingredient in appearance of oil being dark) is generally sub-micronic in size when it starts out. And the oil add pack (specfically the anti-agglomerates/dispersents) makes every effort to keep the soot very small. As soot co-joins, it becomes larger and can become descructive in tighter clearance areas. So it is the oil that keeps soot small, and the filter is just along to catch BIG particles (typically 15um and larger with any real efficiency to brag about). Going to a larger filter is not going to have any effect whatsoever on the appearance of sub-micronic soot; it cannot even begin to hope that it would catch particles that small. From a macro view, 100 particles of soot 1um in size would "appear" as dark as 4 particles 25um in size. The filter can catch the big ones, but it can never address the small ones. Even bypass filters are not typically efficient at sub-micronic particulate.
In short, with conventionally filtered oil, soot size is not a matter of the filter selection; it's a function of the add-pack strength. I have personally run conventional oil out to 10k miles, and got stellar UOA performance (wear, insolubles, contamination elements, etc), indicating that the add-pack was still doing it's job. Frequent OCIs make oil "look" cleaner, because the rate of soot production is generally constant. If you change oil often, it will appear cleaner, even though the alternative (sub-micronic soot loading) has no real detrimental effect when properly monitored.
Additionally, filter makers will not warrant applications that you perceive to be "better", but they have not validated. If you don't use the filter they spec for your application, they are not bound to warrant the product should any failure happen; the burden of proof would be upon you and not them, per Mag/Moss ACT case law decisions. If you believe that the filter alternative would not fail, then this may be of no consequence to you. (I personally use some filters in un-spec'd applications; I'm willing to take the risk at times. However, it's a matter of convenience, not efficiency or capacity, I'm after.)
Caveat emptor.
