Oil Change Interval vs. Need for Valve Blasting

As most of us are well aware by now, Direct Injection engines are prone to developing crud accumulations on the backs of the intake valves and the surrounding area in the head. Unfortunately many of us have had to have our engines partially disassembled and 'walnut shell blasted' or used other abrasive means to remove the deposits.
Several causes for this problem have been extensively discussed. It seems the deposits are the result of condensed crankcase blow-by gasses which are not dissolved by gasoline. Gasoline no longer runs through the intake area of a direct injected engine.
I have a theory that those with longer oil change intervals may be more likely to develop deposits than those with shorter intervals. This poll will help me further explore that possibility. It is decidedly unscientific, and overly broad, but will help me decide if further research is warranted. Probably its biggest faults are that it doesn't control for driving style and mileage. Regardless, it's a start.
If you have been using Techron or any other fuel system additive respond as if you did not.

Please select one condition most applicable to you:

EDIT: SORRY, WHEN I WENT TO POST THE POLL I GOT A MESSAGE SAYING I HAD ONLY TEN MINUTES TO MAKE UP THE POLL. BY THE TIME I GOT IT DONE I WAS OVER THE LIMIT. WILL TRY AGAIN LATER!

Poll fail.

Voice of that experience - prepare the poll in a Word document ahead of time, then cut and past.

DSX - good concept. Better luck setting up the poll.

mine only had it done once at 137,000 miles. I change oil like i change my undies. When they can walk to the basket...

Just kidding every 8,000 miles

Mine is mixed-mode. For the first 3 years I went full factory intervals, then I switched to 7500 miles (or sometimes less) between changes afterward. My valve problems likely showed up around 60k miles.

I bought the car with 15k miles on in, right after the original owner had the oil changed according to the BMW maintenance schedule. Since then I've changed the oil every 5k miles, 3 times now. At the moment my car has 32k miles. I am planning to keep changing the oil every 5k miles. As far as valve cleaning goes, it will be done at 50k miles or when I begin to feel the usual symptoms of carbon buildup, whichever comes first.

I'll expect this poll as soon as I see DSX's pictures from CTC4

Originally Posted by AnotherGeezer

I'll expect this poll as soon as I see DSX's pictures from CTC4

Ouch.

it would be nice to see pics of what they look like at 30K miles

I plan on changing oil every 7500 miles or 6 months, I got my 07 335 HTC in nov last year and put 1000 miles on it to date, its my weekend car,

my 4runner is my travel vehicle when I call on customers

Hondo

7500k for me bro and you saw mine I also didn't start mods till right before WB. So 99% of those deposits were probably stock

What about boosted vs stock? I can't believe that this wouldn't be a factor as well.

Originally Posted by galahad05

What about boosted vs stock? I can't believe that this wouldn't be a factor as well.

Could be, I know with higher PSI you want to change plugs @ 25-30K intervals to prevent misfires. Don't have enough mileage for poll.

So maybe DSX's (eventual) poll should be limited to people who are completely stock. This to help eliminate extra variables. Either that or perform Statistical DoE (Design of Experiments).

I think if there is a poll a better reflection of users would be those that:
drive the car hard all the time
drive the car hard part of the time
don't drive the car hard

oil changes per CBS
oil changes approximately 7500 miles

modded car
stock car

It is known that you get blow by under vacuum but how much is unknown (BMWs PVC valve don't seal completely) and blow by under boost.

For me my answers would be
don't drive the car hard
change oil every 7500 miles
slight mod (JB+)

I am sure we can work this out but do think a more comprehensive poll would help since there are more variables than just one or so. That would give us all a lot more information to see if there is a trend...

Originally Posted by CarlsonTheFlyer

As far as valve cleaning goes, it will be done at 50k miles or when I begin to feel the usual symptoms of carbon buildup, whichever comes first.

Quite the coincidence. Just got back from a dealer service yesterday and they mentioned the carbon blasting (@ $750) to me. First I have ever heard of it so I checked the forum and there it was, right at the top. In my SAs defense, he said that the blasting and fuel induction service were optional and that they had no indication they were necessary at this time. Rather, he said, they were indicated by time and mileage (2007 E90 335 w/ 70k miles).

So, the question is, how will I know if I need this? What are the symptoms of carbon build-up? As far as I can tell, the car is running the same as it was when I got it three years and 40k miles ago. Could be a gradual thing that I haven't noticed or just not a problem.

Originally Posted by Psi 5

Quite the coincidence. Just got back from a dealer service yesterday and they mentioned the carbon blasting (@ $750) to me. First I have ever heard of it so I checked the forum and there it was, right at the top. In my SAs defense, he said that the blasting and fuel induction service were optional and that they had no indication they were necessary at this time. Rather, he said, they were indicated by time and mileage (2007 E90 335 w/ 70k miles).

So, the question is, how will I know if I need this? What are the symptoms of carbon build-up? As far as I can tell, the car is running the same as it was when I got it three years and 40k miles ago. Could be a gradual thing that I haven't noticed or just not a problem.

If these two threads don't make you want to do it. Nobody can really help you
http://www.bimmerfest.com/forums/sho...d.php?t=678670
http://www.bimmerfest.com/forums/sho...530&highlight=

Originally Posted by Zeichen311

Ouch.

He must have been walking around with a fake camera, fooling us all into thinking that he was taking pictures. I do remember him springing up the rock, above the Mt Washington parking area, not unlike his favorite barn yard animal, to take said pictures.

My post makes 19 replies and 470 views for a failed "poll" thread. Not bad.

Originally Posted by SuperTerp

If these two threads don't make you want to do it. Nobody can really help you

Saw both these threads before posting and they are certainly compelling. That said, it doesn't answer the question of how you would know if your engine looks like this or what impact it has if it does. Or is the argument that every single 335 looks like this whether you have pictures or not? And what is the practical risk of doing nothing about it?

The comparison for me is engine oil sludge from which my E39 540 suffered. The dealer and one indy wanted to thoroughly clean it out (for some outrageous amount of money). My trusted indy said not to worry about it unless I actually noticed some performance decrement. I didn't and the car worked wonderfully for 100k+ miles after the dealer's diagnosis.

You don't have to do anything unless you see symptoms--hesitation, misfires, noticeable performance degradation (typically high load low rpm), or progressively worsening gas mileage.

Originally Posted by Psi 5

Saw both these threads before posting and they are certainly compelling. That said, it doesn't answer the question of how you would know if your engine looks like this or what impact it has if it does. Or is the argument that every single 335 looks like this whether you have pictures or not? And what is the practical risk of doing nothing about it?

The comparison for me is engine oil sludge from which my E39 540 suffered. The dealer and one indy wanted to thoroughly clean it out (for some outrageous amount of money). My trusted indy said not to worry about it unless I actually noticed some performance decrement. I didn't and the car worked wonderfully for 100k+ miles after the dealer's diagnosis.

I only noticed some light rumbles at idle I didn't care for + I'd known about the issue. Frankly $450-750 isn't that much to let princess feel as pretty on the inside as she looks on the outside People have different priorities and we've seen plenty of cars go 100K without it, I just wouldn't add undo stress for that small amount of money.

Thanks - that is helpful. I'll ask my indy about it next time I need service. My car will go out of the CPO warranty and extended service in a few weeks so that's it for the dealer!

I may try this in a couple of years, perhaps at the same time as spark plugs, and I'll keep an eye out for any developments in OCC designs in the meanwhile. I'll also cross my fingers in hopes that more indys will acquire walnut shell blasting capability by that time.