angrypengu

As I suspect, embarrassingly, some of you have figured out about me, I am a pretty technical person and am a self professed car enthusiast who likes to tear things apart and to understand them.

TLDR: Don't change your oil early. It is unnecessary.

Deep dive: The SQ5 oil analysis found in this thread https://www.audiworld.com/forums/q5-...lysis-2940685/ is incredibly useful for all of us with the Audi A8 55 model. It's the EA839 engine which is the same as on the SQ5, and on the B9 S4, the A6, A7 etc. It is very surprising to me that a 0w20 oil managed to not only survive to the prescribed manufacturer interval but to do so well.

It is important to note, that changing engine oil too often in our direct injection engines is actually bad. This is something that I only recently learned. Previously, on my last Audi, I would go with 3000 mile oil intervals (or 5000 at times) because my thought was that engine oil shears due to fuel dilution and other factors, and this promotes more blowby and thus more junk to be attached to our intake valves.

I was surprised to learn from an oil industry veteran (found on BITOG) that virgin oil is actually very volatile. There is more blowby produced as a result of an oil change than oil that just sits in an engine for the prescribed interval. The Blackstone UOA in the SQ5 thread gives me assurance to leave the oil until the 1 year xxxxx mile mark. So I thought I would share.

I have been monitoring the PCV valve in my D5. There is still oil in the PCV tubes which means that the engine air oil separator is doing a good job, but albeit not a great job. I believe that with PEA additives in fuel (namely here in Canada with Shell Premium) that since the additives survive combustion and would join the blowby through the PCV valve and past the intake valve that we should be OK.

I have been an avid proponent against the use of catch cans, but I may evaluate it this time around again. There are no threads I read anywhere that have any intake valve carbon buildup concerns on the EA839, but it's still early.

gk1

Not being an expert, but I would have thought the initial volatility of virgin oil would disappear as soon as the oil was brought up to temperature? Maybe not....
I remember this being brought up a while back on the forums, might have been on the C6 A6 with the very carbon buildup prone 3.2. The argument was that too frequent oil changes were causing the carbon buildup. However I do not think anyone proved that to actually be true, all just theory. I actually had the carbon buildup issue on my very well maintained C6 A6 3.2 with 5k intervals but at that time almost every 3.2 had the problem. Whether they had 12k/10k/5k/3k or whatever OCI. At around 18k miles I got an MIL and Audi cleaned the intake valves and performed a software change to effect valve overlap, and at that same time I started religiously using Redline SI-1 (high PEA as you mentioned). I went another 14k miles without any issues before trading it but who's to say it did not develop issues again later?
Since then I'd like to think Audi has improved their carbon situation, I know the RS5 V8 motor was one of the worst. I however still religiously us Redline SI-1. I know many will balk that it does not wash over the intake valves and thus does nothing for DI motors, but I now have 68k on my SQ5 and 35k on my S6 using this method and so far no carbon issues to report. They even had the SQ5 supercharger off recently to replace a pcv valve and thermostat and while I forgot to have them specifically look at the intake valves or provide pictures I'd like to think if they saw a significant problem they would have mentioned it. (maybe not though) Anyway I will continue my silly tradition of SI-1...damn the naysayers.

angrypengu

I'm an educated user, but I certainly would not call myself an expert! I would agree with you that the initial volatility should disappear very shortly, but the question is whether or not the amount of carbon buildup on the intake valve would be greater than if the oil was left and not changed in the first place. The oil industry expert certainly said that as per the testing they did (I apologize, I don't remember which oil company) that they believed too frequent oil changes were the cause of a lot of premature carbon buildup intake issues. I certainly have my reservations because I don't know of too many people who even know what direct injection is, let alone do more frequent oil changes. Most folks are cheap with their car, so that doesn't pass my sniff test. That said I am certainly not an oil industry professional/expert, so I'm deferring to his guidance there.

Redline SI1 is absolutely a fantastic. Very high in PEA, and now there are products like the CRC Intake Cleaner which is chalk full of PEA as well and literally meant to be blown past the intake valve (it's a liquid). I think this time around ownership wise I am much better armed to deal with this, although I do agree with you that I don't think these issues are that rampant anymore. The Engineering Explained Youtube channel made several convincing arguments against Italian tune ups so this time around I find no need to mash the throttle at every opportunity- and his explanation makes sense. When we (D5 folks) mash the throttle, all of the blowby literally gets shunted directly to the turbo, without going through the air/oil separator module, so the name of the game from a carbon buildup perspective is don't do an Italian tune up - or, that is, unless you're having a bad day and want to go fast

That said, certainly NOT a silly tradition of SI1, but I would, as a friendly aside, warn you that I saw pretty significant flashpoint drops after using SI1. It's also why (I believe) the instructions inform users to do an oil change after SI1 is run. The best thing to do (confirmed by me using a boroscope) is to run SI1, but to NOT just do a highway drive. PEA works best when you drive the car to operating temperature/hot/whatever, and then turn off the car. PEA needs time to sit/work on the intake valve, and thus putting in a can of SI1 and then doing 500 miles on a highway drive has very little effect for active carbon removal. It is also why with the CRC product, it explicitly tells you to let the engine sit for an hour prior to operation after using their product.

Just some friendly knowledge I've gained and want to pass on :-) I enjoy learning about this stuff so if you or others have any points that I can learn from/digest, I certainly welcome it. It's why we're all on this board!

gk1

I do both a shock treatment of a full bottle one tankful prior to oil change time and a continuous treatment of Redline's recommendation of 1.5oz per 10 gals...so no worries there.