Port injected carbon deposits. Is my oil to blame?

Mar 13, 2021
VW 2.5 5cyl.

It’s not the best pic. I can probably get better pics tomorrow since I’m still in the middle of replacing the oil filter adapter.

All of the intake valve have deposits on them. They are super hard like carbon kinda in between oil and carbon consistency. The intake runners near the head also have the same deposits.

Since I run quality fuel like Mobil and Shell, I don’t get why this would be a thing since it’s port injection.

I use Castro 0w40 VW 502.00 spec oil OEM MANN filter, 10k OCI as per VW. I thought this oil had low SAP, which is why I’m confused about the amount of deposits.

I commute 140 miles a day 5 days a week. I’ve put 45,000 miles on this motor since I bough it.
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May 25, 2005
No, I don't think it's your oil.
You mention that you have put on 45000 miles but, how many total miles are on the engine?

VW's seem to have always had some intake runner/valve issues(I'm not saying "problems") with carbon build-up such as what you're experiencing here.

Although I don't think that this amount of build-up would be abnormal for a higher mileage engine however, it may be though for a lower mileage and your type of daily driving.

Your engine may just happen to be a good candidate for an aggressive fuel system cleaning beyond using just using a good gasoline such as Mobil or Shell that you mention.

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Dec 28, 2014
Love to know how many miles. I’d venture to guess you’re using oil, right? Looks like you have oil tracking into the intake (obviously) and mixing with the EGR gases. You could check your PCV valve, but depending on mileage I’d say you have some ring blowby and it’s causing oil to get into your intake.
Nov 16, 2002
I'm not sure how SA impacts IVD's as there was a lot of debate about that a while back with some thinking that LZ study was flawed. I personally don't like oils with a lot of VII's. I now think SA is not as important in regard to IVDs as I once did.

I'm not sure what is going on in this case. 10k mile drains is a bit high for a GDI IMO. Did you use any fuel system cleaner?
Dec 15, 2002
Simpsonville SC
Edy hit the nail on the head with this engine. It should be considered routine maintenance to change out the breather (PCV to some) as they always seem to fail. This either sends a ton of oil vapor into the intake stream or over pressurizes and starts popping seals. One common theory with these older port injected VW engines and IVD was leaky valve guide seals. If overall mileage is high, could be this as well. Your oil choice is fine (I think the 0W-40 leans more mid-SAPS) and OCI is ok with the long distance commutes. I would invest in a UOA @ 5K to see whats up. Right after you change the breather ;).
Dec 24, 2011
North Carolina
I honestly don't see anything to worry about. IMO if you never removed the intake you would have never seen these light deposits and therefore never worried about them.

You can try a new PCV diaphragm or replace the whole valve cover but the way they typically fail is to tear and in that case you will get a MIL on.

502/505 is a full-SAPS oil formulation. 504/507 is mid-SAPS but typically paired with other approvals that are low-SAPS.