Update on G35 oil consumption... catch can?

[OCDriver]

After considering all the helpful advice in this thread, I put in Castrol Edge 0w30 ("German Castrol") at my last OCI.

First, a correction to amend to the linked thread: I originally said I was losing about a litre between 5000km OCI's. I realized I forgot to account for the level difference between OCI's. Redoing the math, it's actually closer to 1.5-2 litres every 5000km.

That being unfortunate as it is, with 2000km on this oil and replacing my PCV valve at 800km after the OCI, I'm still losing oil at exactly the same rate. So, it hasn't gotten any worse, but it's not any better. I'll probably try a 40 at my next OCI.

In the mean time, I want to attack it from another angle by installing a catch can. It may not solve the problem, but it will help me further troubleshoot the source of it.

I've seen a few ways this is done:

1. Sealed can between the PCV valve and the vacuum inlet on the manifold. This theoretically draws most of the nasty stuff out into the can and returns clean-ish vapours to the manifold. I expect this probably won't have much effect on consumption, but I'll be able to say, "yup, that's where my oil is going." The only potential problem I see with this is possibly a slight reduction in the vacuum on PCV (due to it having to travel through the can and additional plumbing), adding more stress to seals.

2. Pulling the PCV valve, plumbing it to a vented can intake, and plumbing the other side of the can to the fresh air inlet. The vacuum inlet on the manifold and fresh air outlet on the intake duct would be capped. This has reportedly seen some success in greatly reducing oil consumption, but having no vacuum on the PCV and only getting fresh-ish, unmetered air seems like a Bad Idea™.

3. Breather directly on the PCV port (no valve) and cap the vacuum port. Obviously, no vacuum and possibly changes the AFR a bit. Still seems like an iffy idea.

What is generally the best setup for this? Are there other possibilities?

 

[SLCraig]

If this is an early VQ35 then the oil consumption is coming from the piston rings. I had a 2002 Maxima that burned a ton of oil. It ran great and I had no mechanical issues with the car at all, but the oil consumption on the 02-03 especially VQ35 was a legitimate issue.

 

[OCDriver]

Yup, same story here. No mechanical problems, just eats oil.

I figure I could improve things a bit with a catch to cleanup the PVC tract.

 

[bandz7]

I had an 04 murano that loved to use oil. Like others have said, basically a perfect car except for that. At its worst I calculated a quart after 700 miles. Then after a Kreen piston soak it improved to 1500 miles for a while until I got rid of it.

 

[benjy]

unfortunately manufacturers consider a qt on a thousand ok!!! todays lower viscosity oils burn off quicker + oil contamination hurts mpg's as well as serious carbon issues in DI engines. high oil consumption is NOT OK!!!

 

[TiredTrucker]

I picked up a 2006 Cadillac CTS 3.6L about 2 months ago. Had 52,000 miles on it. Learned real quick it was an oil eater. 1 qt per 1000 miles easy.

Dealer had changed oil when I bought it, but I did an engine flush and changed oil about two weeks later, along with putting a Elite Engineering E2 catch can on the PCV line. used a 5w30 synthetic. It still consumed a lot of oil, but most of that "consumption" was oil going thru the PCV line. The catch can captured about 1.5 to 2 oz every 100 miles. I was really concerned.

At 2000 miles on that oil, I did another engine flush and this time changed oil using a 10w30 synthetic. Two weeks and around 400 miles, and oil level is staying at the full mark. Catch can captured about 1.5 oz total in that time. Seems the two engine flushes got rings unstuck. I am assuming they were, in that there had to be a lot of blowby to cause so much oil to go thru the PCV.

Either way, the two engine flushes must have done well. Consumption is merely a fraction of what it was before. Almost non existent now in comparison to when I first got the car.

 

[OCDriver]

Flush = oil change?

 

[SatinSilver]

No, two different things. Gunk sells an engine flush as do other companies. Pour the product into the engine, let it idle 5 mins or so then let the oil drain out and do an oil change.

 

[CBR.worm]

Is the car a 6mt?

I've seen a direct correlation between 6MT's and oil consumption, particularly the rev-up motors which didn't arrive in the G35 until '05.

I've also found a direct correlation between high RPM and oil consumption. If I drive easily, I can use less than a quart in 3k miles. On a track I can go through a quart in a day.

 

[TiredTrucker]

Originally Posted By: OCDriver
Flush = oil change?


Not for me. I ran the Amsoil engine flush product in the engine as they recommend and did an oil change. So on one level, yeah, flush = oil change in that they were done in conjunction with each other.