Hey guys, I may or may not have screwed up. The 350z I bought might have a particularly bad oil eating problem.

Runs great, pressure at idle is just under 30psi on the gauge, but after driving it around town yesterday I checked the oil level and unless I'm severely misreading it, it started at 90% of full (yesterday morning cold) then this morning it looked like it was at 30% of full. It has a small leak looks like the left valve cover, but my real concern is the smoke coming out the pipes. I recorded a small video just now and I'd like some opinions.

https://youtube.com/shorts/GoDXh7mG7Xc

Oil looks clean, coolant in the res looks clean, so not sure what it could be

It has no cats, and a somewhat rough tune (running but not refined, takes 10 ish seconds on the throttle from cold to idle and takes a couple tries after a rev to stablize at idle), I'd like some opinions.

 

No way to tell from descriptions or even video. Get a leakdown test done on the VQ...

 

forgot to add prev owner says compression was good all around for what that's worth

 

Unless the previous owner provided you with a written report on compression testing, it's all heresay. Did you get a PDI before you purchased?

 

This. ** And, a compression test only supplies compression #s, which, by themselves mean very little. Leak down testing identifies where you're losing compression. So, no matter what the seller says, wise to take it to the next level since you've already ascertained it's losing/using oil. A leak down test can help pinpoint a ring, valve, etc. issue.

 

What year Z is it? How many miles on it? AT or 6MT? Any other mods aside from "No CATs" and a rough tune?

When you checked the oil, how long did you let it sit for before checking? Were you on level ground? 350Zs are notorious for being difficult to get an accurate read from the dipstick.
Cheers!
-Icer

 

Watching the video, yeah it does look like it's burning some oil. How it's entering the combustion chamber is debatable. As suggested, a leak down test will help determine this. Typically it's either worn rings or the valve stem seals.
Good Luck!
-Icer

 

yeah thats what Ive been hearing. Will have a shop with the right tools do some tests, depending on what the diagnosis comes back with ill either fix it or just buy a low mile engine. It's a 6MT Enthusiast and I have the mods that's on it in my profile.

I'm 80% sure I read the stick right. I've been driving an Auto 04 G35 and doing all the maintenance on it myself. It's just weird because when it was "90%" was after a 2 hour drive home and another day of commuting/around town shakedown driving. So it seems like when it's at constant revs it doesn't burn nearly as much, but around town driving with constant changes in revs it burns up. Making me think valve seals but if the stick is right id think thats a lot more burn than valve seals can do

 

One last thing to check is the PCV system. VQs are known to ingest some oil through the PCV hoses at the intake. For this reason, I installed a baffled catch can and I can confirm 1st hand that the catch can is doing it's job. But to be clear, it's only catching maybe 1/4qt or less of gunk between oil changes (3500-4000mi). If you're losing almost an entire quart after only driving 500mi or less, no oil catch can is going to fix that. But more importantly, make sure the PCV valve is working properly, if it's stuck closed or clogged, this will cause pressure to build in the crankcase and can lead to oil leaks and exacerbate oil burning. You can also try a thicker/heavier oil (40 weight). If the stem seals or rings are toast, this won't fix the problem entirely, but you might be able to at least slow it down to a tolerable level.

TLDR: Check PCV valve and hoses. Make sure they are in good working order. Try a thicker oil as a band-aid measure.

Good Luck!
-Icer

 

No way to tell from descriptions or even video. Get a leakdown test done on the VQ...