Originally Posted by pitzel
Originally Posted by superangrypenguin
Thanks for the info. Do you have any studies you can point to which have either specifically looked at this issue or has proven this specific theory that more aggressive oil changes may lead to an increase in carbon buildup for intake valves?
https://www.jstor.org/stable/26273486?seq=1#page_scan_tab_contents /
https://www.sae.org/publications/technical-papers/content/2016-01-2252/
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Using a vehicle equipped with a 2.0L turbo GDI engine, the mechanisms leading to deposit formation have been studied and analyzed, and found to be a combination of engine oil, engine-wear elements, unburned fuel, and exhaust gas contaminants. The rate of accumulation was also found to be affected by engine lubricant formulation variables.
https://www.sae.org/publications/technical-papers/content/2002-01-2660/
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A test cycle was devised to accumulate deposits over a 30.000km oil drain interval and was conducted at an independent vehicle test track facility....The project clearly demonstrated that lubricant formulation has a significant impact on the level of IVD formation. There are indications that the additised fuel may also have had a beneficial impact on IVDs. The field test program also showed that despite the build up of deposits on the intake valves over the 30.000km test no detrimental effect on drivability was experienced with the Ford DISI engine technology.
Its definitely not a binary "XYZ changing oil overly frequently is 100% at fault for the problem", but it is fairly clear that the lubricant, and its volatilization does play a very significant and crucial role in deposit formation. Optimizing the exposure of the intake to such oil distillates, while preserving the distilland's ability to provide ongoing lubrication is obviously the goal of OCI optimization.
The industry, of course, faces an interesting battle. Very long OCI recommendations by manufacturers are often written off by maintainers as serving the manufacturer's self-interests and ignored (go to any BMW enthusiast forum, and you'll probably be told that the BMW recommended OCI's are "insane" and not to be followed). The oil change is also the only time at which most cars in North America receive anything that resembles a maintenance inspection as most people "run to fail" otherwise, so there are brand reputation risks (and even legal risks given the proliferation of SUVs with their well known higher sensitivity to tire maintenance) with having vehicles go extended periods without maintenance inspection. Retail oil vendors have little interest in pushing long drain intervals for obvious reasons. Widespread UOA to support very long drain intervals just isn't practical or fitting with the North American economic model of maintenance (nobody would accept visiting a Jiffy Lube on Monday, paying $60 for a UOA, and being told to come back in 2 weeks once their UOA test results came in). So the efforts appear to have been heavily aimed at "harm reduction" -- very high oil specs even for oils that will mostly be used in "legacy" vehicles. Supplemental port fuel injectors (Toyota et al). And maintenance minders that guide the use of much longer than traditionally employed OCIs. Centralized maintenance databases also allowing manufacturers to crack down on their "official" servicing networks that recommend inappropriately low OCIs with cheap/bulk out-of-supply chain acquired oil as a maintenance services marketing scheme. As well as auditing for quantities of official supplies ordered against recorded-as-dispensed OC's. The bias of "more oil changes is always better" seems to push even ordinarily rational people into refusing to fully investigate overly frequent OC's as a significantly contributing root cause of intake occlusion far in excess of what was experienced by the manufacturer during the manufacturer's own internal testing.
I appreciate this information. Do you happen to have the SAE study in full? If not I'll fork over the funds to pay for it. It's just unfortunate because the information in the abstract is nothing new to me. I'm keen to see if that study examines the issue at hand.
I agree with you that virgin oils have a level of volatility that is worrisome to me. What I'm trying to figure out is the correlation to intake valve buildup and whether or not that resultant intake valve buildup of carbon is worse off than engine oil that has been sitting in a motor for a while being subject to the usual stressors, which in several gasoline direct injection applications involves turbochargers. The recent use of thinner oils also is worrying for me.
On the one hand your claim appears to be backed up by common sense in regards to virgin oil volatility, but on the other hand the other poison is what I talked about in this post.
I'm trying to discern what is the least evil, so to speak.
Edited to add:
Most folks don't know that engine oil on turbofan engines do not require changing. I'm certain most on here do. In particular for my question at hand I wonder if it's better to wait until a prescribed oil change interval or to change things half way. In my case with 508.00 engine oil at a 0w20 weight, I'm going to have to seriously wonder if I wait for the 15,000km, or change it at 7500km. That's what I have been trying to figure out over the last few months.
Deal with virgin oil volatility or used oil volatility? I have no idea and as an engineer I'm trying to see if there are studies on this.