Hello,

I’ve just recently changed my oil and for the last three changes, I’ve been low on oil. The amount is about 1-2 quarts low. As a result, I’ve been researching the purpose. I’ve read somewhere that an old, unmaintained PCV valve can be the reason. Also, more recently, I stumbled upon this article:

http://mywikimotors.com/vq35de/

Now I don’t know how reliable this is because it makes some interesting, sometimes far-reaching claims. There is a section that suggests that the catalytic converters will break down as a result of using subpar gasoline. Compression is reduced and excessive fuel and oil consumption ensues.

This post is for anyone who has encountered this problem with success or anyone who has installed upper high flow cats. Note, this does not apply to the lower cats.

2008 M35s
VQ35DE

More likely the reverse, cats in good shape expect about 98-99% burned product coming into them that will not burn again, when the crap fuel and oil not burned hit the converter then it flares up massively in temperature to burn those and kills itself in the process, sometimes it can even melt portions of the matrix and those are pretty much dead after that. Where the strong sulfur smell comes from, the cat overloaded to do that.

Subpar fuel with say ethanol in it tainted by water will misfire as water will not burn and the misfire adds to cat overtemperature as it then has to burn the leftover fuel that did not burn due to the misfire.

There was also a string of V6 around that time ('08?) that had improper plating in the upper cats that came flaking loose to backflow backwards back into motor at overlap to then erode the cylinder walls and rings due to the hardness of the basically ceramic materials used in the cat lining.

Look it up, should be pretty easy to find something on it. Ford had trouble with the same thing too around year 2K.

I may be wrong, the year problem looks like it ended around '06.

Nissan TSB# NTB08-023

amc49,

Thanks for the reply. I was going to correct my initial post. It was bad fuel that was causing the upper cats to collect the ceramic powder that would then enter the cylinder and scratch the walls.

I’m going to try what I’ve never believed in and try an additive for the oil. It claims to fill in the scratches and restore compression. I’ll change the upper cats to HFC’s prior to the additive treatment. One thing is for sure though. I’m burning oil and won’t expect 250,000 miles if I don’t act.

Last year my upper cats disintegrated, I am not sure of the exact cause, it was on a long trip over rough poorly maintained roads and my exhaust system took a big hit on the road. Might have been that combined with oil damage. Anyway, the point I wanted to make is when the upper cats start to fail and break up exhaust gas reversion can suck parts back into the rear cylinders and then the engine is toast. It takes a few weeks after that, but the bits of cat act like sandpaper inside the cylinder. If you think you are having cat failure, act now, don't wait. I didn't notice until it was too late.

Rob bb

Thanks for the reply. Yeah it sounds like that spill you took that damaged the exhaust components.

I’ve just replaced the PCV valve. The car seem to function better as the engine speeds up. I’ll post again after I’ve put some miles on this oil.

Has anybody had any luck with aftermarket cats?

Here are some videos I found. Note that the 350z has the same vq motor as the m35. Also note that these are vehicles that kept the stock exhaust with the exception of the upper cats.

https://youtu.be/spqUmRKBswI

https://youtu.be/D903n80wLzI

https://youtu.be/kMgs6ZxqNBw

Vanv wrote: ↑

Mon Feb 17, 2020 8:57 pm

Has anybody had any luck with aftermarket cats?

Could you please update your profile with a valid email address? Thanks!

Rogue One wrote: ↑

Wed Feb 19, 2020 2:23 pm

Vanv wrote: ↑

Mon Feb 17, 2020 8:57 pm

Has anybody had any luck with aftermarket cats?

Could you please update your profile with a valid email address? Thanks!
rvanvorh.png

Updated

Having owned several VQ cars, currently a VQ35DE rev-up 350z and a 2008 M35S VQ35DE (regular DE 6500rpm redline) I can say that these high compression engines tend to see more oil consumption than most low compression cars (under 10:1). Combine that with the fact that since Nissans/Infinitis are Japanese most people will NOT do any type of preventative maintenance and treat them like cheap hondas under 100k. Combine that with aggressive driving prior to you owning the car. Combine that with using cheap fluids, conventional oil, etc...

Lots of factors to consider. A lot of threads in the 350z and G35 forums about oil consumption. I would strongly recommend you research there since we share the same engine. Lots more technical information and it all carries over to the M platform.

What's my experience? My m35 is at 150k and it did burn a little but not much. I got it to stop burning oil by adding .25 qt MMO and .25qt Lucas on top of the 5 qts. at each oil change. I was very objective about this finding and I'm sure this might spark debate but that worked for me and I'm sticking to it. And even though the m35 is my daily I do beat on it.