Originally Posted by pitzel
Originally Posted by john_pifer
You're saying more frequent oil changes cause more intake tract buildup?
How so?
Virgin motor oil, prior to significant in-service use, has the highest rate of evaporation. So when an engine is exposed to longer OCI's, less initial evaporation takes place under engine operating conditions, and hence, fewer intake valve deposits due to such.
The OEMs have invested considerable resources to prod their customers into using longer OCI's, *and* have mandated far higher quality oils that are less susceptible to early evaporation. They've also cracked down considerably on their own dealer networks that frequently filled cars with out of spec lubricants for cost efficiency or marketing purposes.
A big problem for the OEMs in replicating the intake building issues was simply replicating the issue. As OEM engineers simply could not fully appreciate how engines are maintained in "the real world" which often includes the use of poor quality lubricants changed overly frequently. When the topic came up a few years back, I did a post here where I meta-analyzed a several hundred page thread of an enthusiast forum in which there were complaints of the intake clogging -- every last complainer had a high likelihood of maintenance that was not per spec, ie: overly frequent oil changes and/or high susceptibility to lubricant fraud.
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What comes through the PCV is liquid oil mist, not evaporated oil vapor. Therefore, Noack volatility has no direct effect on the intake valve deposits (IVD).
Of course there's evaporated oil vapor in the PCV gas stream. And if "Noack volatility" has no effect, where the heck does the oil evaporated in a NOACK volatility test end up, if not recirculated back into the intake.
i used to change with m1 every 1500miles in my extreme obsession days in my 09 cts 3.6 di,add that to very short trips and now i see why i started to have cold start misfires,
and lost 2 converters beacuse of that also? both in the 70-80k miles