Please list engines that are prone to piston/ring deposits, varnish, or sludge.

[Glenda W.]

Just looking for a simple list of engines that have cleanliness problems with normal oci’s. Here are 3 that I’ve owned and/or maintained.

2018 Subaru Outback 2.5-stuck rings

2016 Acura RDX 3.5-varnish front head

2017 VW Tiguan 2.0T-stuck rings

 

[Jetronic]

GM ecotec 1.5 . Stuck rings, varnish and stuck pcv (mounted inside the valve cover).

 

[duck__dodgers]

Isn't easier just to do it the other way around???

engines proven to either stay clean with reasonable maintenance or known (anecdotally) to tolerate abuse from Normie owners.

 

[SC Maintenance]

Unsure if its the engine itself or longer OCI, but 2.4 Tigershark and 2.4 Theta ii I think are both known to sludge?

 

[tired]

This would be a great thread for the wiki function that many forums have—a top post that can be edited forever to add new engines to the list, so future readers don't have to read 100+ pages of banter and bickering to find what they're looking for.

 

[JTK]

GM ecotec 1.5 . Stuck rings, varnish and stuck pcv (mounted inside the valve cover).

Agreed. It's pretty much any GM GDI 4cyl it seems.

 

[panthermike]

The Nissan 5.6 (VK56VD) has been known to have sludge issues when not kept up well on oil changes.

 

[Blagoje]

Hyundai Gamma GF4D 1.6L 4-Banger

 

[duck__dodgers]

Yes, for gunk when sticking strictly to the owners' manual: Land Rover Ingenium 4-cylinder engines (>70,000 miles).

 

[1lieutenant]

Acura 3.7L engine. Carboned rings, factory authorized short block or just ring replacement
Usually approaches 1 qt per 1K miles or more at approximately 60K miles

Oil(s) used:
Mobil1 5w-20 AFE
Pennzoil Platinum 5w-20
Castrol Edge 5w-20
5K intervals

 

[dadto2]

Volvo 2.5 I5 model years 2013-2016. The ring design is prone to carbon buildup.

 

[Glenda W.]

Toyota 2AZ-FE and 2AR-FE-stuck rings



Honda has issued Technical Service Bulletins (TSBs) and extended warranties for some models (like certain 2008-2012 Accords, 2008-2013 Odysseys, 2009-2013 Pilots, and 2012-13 Insights) experiencing excessive engine oil consumption, often caused by carbon buildup on piston rings.

 

[Wheel366]

Just looking for a simple list of engines that have cleanliness problems with normal oci’s. Here are 3 that I’ve owned and/or maintained.

2018 Subaru Outback 2.5-stuck rings

2016 Acura RDX 3.5-varnish front head

2017 VW Tiguan 2.0T-stuck rings

How many miles on the Outback before problems started? I have an 18 Legacy with the same engine that has had 6m/6k oil changes it's whole life minus a few 6m but much short mileage the first year or 2. By the time I started doing oil changes (the third one for the vehicle), I had 9,264 miles and the fourth OC was 12,234. Both those used M1 AFE. Since then, it has been Steady M1 EP and 6k changes. I'm at 74,019 now. The first 2 changes were done at the dealer and while I may have paper records, they aren't listed in my mysubaru account. I am planning on running VRP in it, but I have 2-3 more jugs of 1 EP that I want to get through before I do the 4 VRP as a possible preventative measure.

 

[JTK]

I would add the Nissan VQ35DD to the list.

 

[Glenda W.]

How many miles on the Outback before problems started? I have an 18 Legacy with the same engine that has had 6m/6k oil changes it's whole life minus a few 6m but much short mileage the first year or 2. By the time I started doing oil changes (the third one for the vehicle), I had 9,264 miles and the fourth OC was 12,234. Both those used M1 AFE. Since then, it has been Steady M1 EP and 6k changes. I'm at 74,019 now. The first 2 changes were done at the dealer and while I may have paper records, they aren't listed in my mysubaru account. I am planning on running VRP in it, but I have 2-3 more jugs of 1 EP that I want to get through before I do the 4 VRP as a possible preventative measure.

Mine started at 60k. My friend who uses only M1 EP made it to 120k before it started using oil.

 

[SC Maintenance]

known to have sludge issues when not kept up well on oil changes.

Isn't that sort of true for any engine? Not saying the VKDD is or isn't. Which again is back to my question in #4 - are those engines really that bad or did the OEM push the OCI?

 

[Wheel366]

Mine started at 60k

And if you don't mind me asking, what where your OCIs like AND which oil(s) did you use? Just trying to stay on top of this potential issue.

 

[SC Maintenance]

I would add the Nissan VQ35DD to the list.

You ran yours to what - 100K? Was it pretty sledged up? You were doing pretty short OCI as well due to the chain correct?

 

[panthermike]

Isn't that sort of true for any engine? Not saying the VKDD is or isn't. Which again is back to my question in #4 - are those engines really that bad or did the OEM push the OCI?

Fair point and I would agree that yes, all engines are susceptible. I think the 5.6 DI is maybe a bit more sensitive than some. I recall our '17 Armada dirtied the oil shockingly quick. Of course, color is not scientific but I've seen some good videos on YT of sludged up VK's.

I also believe that the VK56's are great engines.

 

[Glenda W.]

And if you don't mind me asking, what where your OCIs like AND which oil(s) did you use? Just trying to stay on top of this potential issue.

Full details

Thread 'Valvoline Restore and Protect Oil Burner Test Results'

Mar 16, 2025

Just passed 5k miles on my 4th and final oci of Valvoline Restore and Protect for a total of 20k miles. It’s been hard to keep my mouth shut but here are the details and results!!

2018 Subaru Outback that I bought new. Started burning oil right at about 60k miles. Before that it only used about a 1/4 quart in a 5k mile oci. It started using 1 quart in 5k miles and steadily increased to almost 3 quarts in 5k miles. I was adding a little over a quart every 2k miles when I started this test. I have done every service myself on this vehicle including the pcv valve on time. I’ve only used a...

• Glenda W.
• Replies: 560
• Forum: Passenger Car Motor Oil (PCMO) - Gasoline Vehicles

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