Any problems with acid build-up or oil consumption?

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8,467
Location
Colorado
If a person starts to extend oil changes beyond 3000 miles (using a good oil like Schaeffer's), are there any problems with acid build-up or other harmful chemicals that cannot be removed by the oil filter? A mechanic once told me that even with synthetic oils, beyond 3000 miles there would be enough acid build-up and other chemical contamination build-up to make necessary an oil change. Perhaps this would only be true if a person was doing mostly short trip driving. Also, I personally have never gone much beyond 3000 miles for oil changes. But I noticed in another post that Gary Allan said that whenever he went past 4000 miles on an oil change, regardless if he was using Mobil 1 or a conventional oil, his oil consumption would increase greatly. I found it interesting that he said that this happened even if he was using Mobil 1. Do motor oils start to break down after 4000 miles?
 
Messages
6,388
Location
Washington St.
1) Filters do not remove chemicals, only particles (some bypass filters do absorb a small amount of water). 2) Look at all the oil analysis results. Every time you see a positive TBN (Total Base Number), which is every one of them, you see an alkaline reserve...no acid is present nor possible in these oils. Any other contamination is also shown in the tests, so you know what you have. 3) Some engines, some driving styles, some driving conditions, some oils will shear down to a lower viscosity after a few thousand miles and be consumed slightly faster. Volatility of the oil allows some to vaporize, but I don't know if this increases with useage. 4) I trust that mechanic knows a lot more about wrenchin' than he does about lubes. Ken
 
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