How many miles on synthetic motor oil?

[Prototyper]

My research indicates that your common gasoline engine can be driven about 12,000 miles between oil changes before contaminates become a concern for induced wear. Some feel a filter change half way is a good idea. Any experiences with extend synthetic oil change intervals?

 

[evelrod]

As many of the members here know, after I retired I worked part time for my ex crew chiefs industrial air compressor company. Part of my duties was to determine why many of the customers were having lubrication problems with some very large rotary and screw compressors. What I found was the service intervals for lubrication changes (synthetic oil) exceeded the oil filters ability to adaquately flow oil at the proper flow rate (no bypass on most)...cure, change the filter at mid point of the oil change interval...problem solved. Based on my admitedly limited experience in the field, I am not at all convinced the "engineers" that concocted the service intervals used much more than a educated guess considering that after many calls, they altered the oil filter change intervals to fit the actual conditions in our area.

Cannot address statements about Toro or the "fact" that oil filters get better with use (??? of course it gets "better" to the point it "filters" 100%!)...I can say that I change filters with oil changes every time and cut my filters open to inspect them, just in case. Just for drill, cut open a few propriety brands and compare...you will be astounded at what you are relying on to "protect" your investments.

Rod

 

[TheBlacksmith]

Agree that a filter gets better with use, but at the expense of reduced flow/increased DP. Maybe its okay for twice as long, maybe it blocks oil flow or goes into bypass, which negates the purpose of the filter until the next change. Unlike steam turbines and large diesels, cars, light trucks and lawn mowers geenrally do not have DP gauges. It just seems light cheap insurance to change the filter with the oil and one less thing to stay awake wondering about.

 

[patprimmer]

drwebb

From my post 31/03/06

The problem is that you can't predict when it will become restrictive enough to cause the bypass valve to open occasionally, allowing some previously filtered larger particles that have settled in the bottom of the filter canister to enter the main gallery.


Regards

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[evelrod]

Referring to Pat's post---difficulty in determining the point where the differential pressure is high enough to open the bypass---
Not all filters are equal (doh). A high flow racing filter such as a Fram HP-1 has a working DP of around 1 to 2 psi as used on one of my Lotus twincam engines @ ~85psi working pressure in a properly designed race engine oiling system , CLEAN. Dirty, after several race weekends, ~5psi, the point of change in that cars owners regimen. We tried a proprietary filter of ~10 micron capability...DP STARTED at 5 psi! I am not sure of the Fram HP-1, but the equivelent Wix (51515R) that I use is ~40+ micron.

A note, that car was not mine as I still prefer to change oil and filter at no greater than two race weekends, regardless of the DP...(actually I don't even have an extra guage on MY race car).

Rod

 

[optimum]

I run 10K miles in both my escorts, Mobil 1 and quality filters (Baldwin or Donaldson) Both cars rarely short tripped, so always at temp. I have never done SOS on oil, because frankly I don’t care. If they die, I fix or replace. My rule of thumb is dirty oil is always better than no oil. I figure why create twice as much waste oil if its not needed.
The only bad part from synthetics is they degrade very fast where as conventional petrol oils lose properties gradually and predictably. I have some info on it around here somewhere. Basically syth’s are better until they hit high temperature. Temperature will make the properties drop off the chart. Conventional oils recover much better from this and slowly degrade over time. I have also ‘heard’ companies like CAT, do not push synthetics even though they sell it. Cat seems to know of other issues with synthetics over conventional oils. I am not sure if it has to due with emissions or durability.

 

[patprimmer]

optimum.

Your comments re thermal stability of synthetics is exactly opposite all data I have read, and contradicts my first hand experience where synthetic oils have specifically solved problems where overheated mineral oil was causing bearing failures.

Regards

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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.