Extending oil change intervals by changing oil filter frequently

Question

I've got an older car with ~170k miles on it. I typically run a 3-5k miles or 6 months oil change interval, which pretty much always ends up at the 6-month limiter. I do this interval so I can run more viscous oils in the summer and less viscous oils in the winter.

I send a sample of my oil for analysis at every change. I've found that the biggest limiter to my oil life is not the additives being consumed or the oil oxidizing/changing viscosity, but rather particulates from the wear on an older engine.

I might not extend my oil change interval because the savings will be rather minimal, but I would like to know if anyone has experience with changing only the oil filter, not the oil itself, and how it has affected performance, wear, and service intervals.

EDIT: While I am seeking subjective answers regarding perceptions from replacing the oil filter without changing the oil itself, I am adding some structure to help with providing quantitative data as well.

Regarding performance, if anyone has normalized dyno tests comparing wheel horsepower over time between oil changes, and over time between oil changes with a filter replacement, that would be appreciated.

Wear can be discussed with either oil analysis results (ex. metal ppm) or microscopic analysis of wearing surfaces, such as cylinder walls, piston rings, bearings, valve guides, etc.

Lastly, service interval is pretty intuitive, but data backing extended service intervals would help. For example, if the oil change interval was 5000 miles, but with a filter replacement, analysis shows similar results with a replacement at 4000 miles and an oil change at 8000 miles, then the service interval was extended by 3000 miles (8000 vs 5000).

EDIT: As requested, I am posting a link to my most recent oil analysis report from Blackstone Labs. I am unaffiliated and I am not providing an endorsement for their services, simply adding information requested in a comment.

Answer 1

The oil filters mostly get rid of particles larger than 20 microns. You will have particles smaller than this size, independent of how many times you change the filter. Therefore the answer is 'NO'. You won't be able to extend oil change periods by changing filters. At least if your oil change reason is the "report" you have in your hand telling you that you have metal particles. Also because you change oil so frequently, you are replacing perfectly fine filters anyway. So changing them more frequently wont help.

The fact that there are metal particles in your oil, does NOT mean that your oil has gone bad (purely depends on the amount of particles and their sizes but reports dont seem to tell sizes anyway). Also it does NOT mean that your filter has gone bad (again depends on the particle sizes). It is perfectly fine, your particle levels are also 1/10 of what online sources tell as upper limits. (see the oil analysis handbook). If anything, you seem to be changing oil/filter too often!

I calculated that if I changed oil at 5k km(~3k mile) like you do, instead of 30k km that I do now, I would have needed to change oil 4 to 6 times more often (at 260k km now), roughly paying the cost of a used newer model car easily for oil changes. What a waste of money that would be, since my engine is working great still, also especially considering people do get over 600k km with this service regime easily! I will get a free car soon :)

Oil filters are designed to last very long time. Because in most cases people change filters with the oil, the filter must always outlast the oil. Car makers have service intervals for 50+k km and 2+ year. So filters must last even longer.

Actually, the so called "filter life" is probably a common sense concept. If there was any kind of "real" limit to filter life, they would have needed to print on the box. Of course they will eventually become clogged etc., but this will take long time to happen. Actually, I am even surprised that filters do not tell 'max X km and max X year' on them, they surely can sell more filters if they do that! (or the values are so high that it makes little sense to write them there). But we mere humans, with our infinite wisdom, like to use our "common sense" to come to strange conclusions.

In either case, I never heard and also could not find any posts online about oil filters releasing particles due to old age or getting clogged so the bypass valve opens. This tells me that since most people change filters with oil change, a normal filter AT LEAST lasts longer than the oil.

About your engine oil. You should NOT use thicker oil unless there is a real reason for it. It is NOT a reason that your engine is old. Having an older or high mileage engine does not automatically mean that it is better to use thicker oil.

In addition, if you use fully syntethic oils. You can get 5W-40 or 5W-50 and then you don't need to change oil due to seasons anymore. Your engine specifications say that your engine should consume 1L oil per 1000KM (1 qt. per 750 miles). I would start with 5W-40 and if the engine is using more than this amount, then try 5W-50

Source: http://www.bimmerfest.com/forums/showthread.php?t=366719

Answer 2

Filters are like this. The more they are used. The more stuff in them. The smaller the holes for oil to pass threw them. The better the filter. But go to long in the filter does not have a overflow. They can clog up & no oil go threw them. Same with a air filter. Look at them the same as you would a strainer at home. The more stuff strained the finer they work. But the slower the liquid goes threw them.

Answer 3

Don't forget to take into account the fact that you'll lose some oil replacing the filter -- the filter itself holds a reasonable amount and on some cars I've had, if you take the filter off without draining the oil you can get quite a bit of oil out through the filter fitting (to the extent that if you undid the sump plug then immediately removed the filter you'd make quite a mess). Other cars have lost very little this way.

This is likely to change the economics of your situation.

Answer 4

You don't mention what kind of car you have so I can't verify they have a product for you, but MicroGreen oil filters are actually designed to do exactly this in addition to extending service intervals. Their argument is at the end of a change interval the structure of the oil is fine and it's the filter that's in sorry shape; exactly what you found. You can look at their site for the specifics of their claim and how to use it. I personally run these because I like the idea of the microfilter acting in tandem with the regular filter, though I still change my oil every 5k miles.

http://www.microgreenfilter.com/

Answer 5

I had the same problem on my Mercedes SUV. The motor oil turned quite black between oil changes, even though the car was in perfect working condition. It didn't consume oil ordinarily, but it used about 1/2 quart if I was very heavy on the gas pedal (flooring it on the highway to 4-5,000 RPM).

My solution was to use Marvel Mystery Oil (MMO) with fresh Mobil 1 in the crankcase, substituting 20% of the oil with MMO. I ran the engine at 3,500 RPM for long (20 minute) stretches on the highway for 200 miles then changed the oil + MMO again. I repeated for 500 miles, changed again, then a third time after an additional 1,000 miles. I also added MMO to gas tank at a rate of 4 oz. per 10 gallons of gas.

The engine no longer burns oil and the oil stays golden clean for 3,000 miles. I concluded that, even though the oil was always changed on time, the piston rings were partially stuck. Today's piston rings are low tension to save gas and I've read they often stick slightly. There was therefore a higher than normal amount of blow-by gases. The MMO freed the rings and improved compression, reducing blow-by and particulates in the crankcase.