Chevron Delo 400LE 5w-40 Syn / 3k mi / 1996 Grand Prix

[92saturnsl2]

Some history, I replaced head gaskets on this car immediately prior to the 2 most recent UOAs. I had a fair bit of coolant in the oil prior to the repair (I purchased the car like this), so I began the UOAs after the HG replacement with the expectation that any residual coolant would trend downward.

Blackstone noted coolant contamination on the last UOA and suggested sampling again at 3k, so that's what I did. Strangely, signs of coolant have increased slightly. I haven't had to add any coolant since the repair, it stays rock solid at the same level in the reservoir, so I'm a bit perplexed why potassium and sodium have increased. The high silicon is a mystery to me, new air filter was installed at the same time as HG repair and intake is in good condition. Could this be due to the small amount of sealers used during reassembly?

I'll probably go another 3k and retest as per their suggestion. Sort of a wait and see approach, but I'll be checking the intake plumbing again in the meantime. Open to suggestions/comments/ideas/etc. I replaced the Delo 5w-40 with Harvest King 5w-30 Synthetic (SN+) oil.

 

[53' Stude]

You didn’t by chance do the upper and lower intake gaskets while you had the engine apart? Looks OK, keep an eye on it though

 

[92saturnsl2]

You didn’t by chance do the upper and lower intake gaskets while you had the engine apart? Looks OK, keep an eye on it though

Yep, both the upper and lower intake gaskets were replaced. Blackstone mentioned sealer-- the lower intake gets a few inches of RTV on the sides where the intake meets the block and that RTV is directly exposed to oil... So I'm wondering if that can cause elevated silicon...

 

[Carbon12]

We had a 2003 Monte Carlo 3.4L with a bad intake manifold gasket. It had been leaking coolant into the oil a long time. After I had it fixed I changed oil and found that the filter was full of sludge created by the water, ethylene glycol, and oil. Looking into to oil fill cap, I saw a lot of sludge under the valve cover as well. It took a few oil changes to get rid of it all. I suspect the sodium and potassium you are seeing (and maybe even some silicon) in the uoa is coming from the oil cleaning up the sludge. I too would do another uoa in 3000 miles as you suggest.