Checked the elbow at the throttle body, and there's definitely oil getting sucked up into the throttle body. I can see it is going into the throttle body from the PCV hose. I know there is sometimes a little bit of oil in there, but what is considered too much? Any ideas what it could be?

 

Absolutely DO NOT use long life or high mileage oil, they contain heavy metals that will destroy the cat.
None is "normal". That much indicates a blow by problem with the rings.

 

Alright, I will do a leak-down test sometime within the next weeks. I have not used any long life or high mileage oil, just use valvoline 5w-30 advanced synthetic.

 

Check the label on the Valvoline it might contain additives like zinc, I don't know "advanced" might mean "high mileage".

 

Nothing in the Valvoline website, just says for DI engines, no mention of Dexos

 

It says Dexos gen 2 approved on the bottle.

It says here that it has 940 ppm of zinc

 

Did a compression test today and everything seemed okay.

The psi I got for each cylinder was:
1 - 125
2 - 135
3 - 135
4 - 130

Since the last time I did a compression test a year ago, cylinders 1 and 4 dropped 5 psi and cylinders 2 and 3 dropped 10 psi. They all went to 120 psi right away and then added just a little bit more pressure when cranking.

All the spark plugs looked just like this:



There's no smoke coming from my exhaust, and the top of the oil fill cap doesn't have any sludge on it anymore.

 

That’s a lot of Zinc, almost 0.1%. By weight or by volume? Something on the order of an ounce, in any event.

Zinc is not a heavy metal. It’s a rather light one, really. But it can still screw up a cat, just takes awhile, apparently, not immediately poisoning it like heavy metals can.

According to this, EPA doesn’t like a lot of zinc in oil, and there are substitutes.

https://rislone.com/blog/engine-oil/...older-engines/

 

That's interesting about zinc. Are there certain oils that contain no zinc or phosphorus in them then? I tried looking at mobil1 and they have 800ppm of zinc and 900ppm of phosphorus in their oil. I tried seeing what was in the ACDelco Dexos gen 2 oil, although I couldn't find anything about it.

I still have the original catalytic converter on my HHR, and it seems to be working alright. I don't think it has ever been tested for emissions though.

Gonna drive the HHR for another week and see what happens to the oil. I've been gaining a few mpg over the past few weeks, so maybe just driving is helping the issue.

 

That looks like sludge on the plug. Is that just an illusion?

This qualifies zinc as a heavy metal.: https://www.ncbi.nlm.nih.gov/pmc/art...%20(32%2C%2045).

According to this: https://www.ratwell.com/technical/OilsWithZinc.html 1400 ppm is in the "normal" range of zinc, meaning 700ppm is low. What I was warning against is the very high content oils like diesel oils and "High Performance" and "classic Car" etc. But, burning oil is always bad for the cat.