On the topic of the milkiness in the oil, right before this oil change, I got a low oil message on the dash and had to top up with a mismatched oil from a gas station, Mobil 5W-30. In addition, I had added ceratec at 170k oil change and then added mos2 at the 175k oil change. I wouldn’t think I’d still be seeing the ceratec (milky appearance), but it’s possible I’m still seeing some of that, the mos2, or the mismatched oil.
I replaced the oil and filter and brought the engine up to operating temp and did a combustion gas in coolant test using a 2 stage syphon tools that draws air from the reservoir through the test fluid. Before testing, I tested the fluid by exhaling while syphoning my breath, changed from blue to yellow. Replaced with fresh fluid before testing. Didn’t change color at all although I really couldn’t draw more than 1.5-2 syphons-full of air before the vacuum became too great and the syphone bulb remained collapsed. I left it for a couple minutes, then repeated the test again. This all was with the engine running. No color change. The syphon also didn’t ever expand after the 1.5-2 syphonings which leads me to think it’s pretty air tight. If there were combustion gases getting into the coolant system, I would imagine they would make there way to the reservoir and the syphon bulb would continue to draw that air in and wouldn’t remain collapsed like it was. (Does that make sense?) I should also mention that upon initial cold start, I ran the test (which I didn’t think would be effective since thermostat wouldn’t be open, not sure if that makes sense) and there was no color change.
With the engine up to operating temp, I performed a compression test on cylinder 4 for the hell of it. More or less same results, 60ish psi on initial pulse, but only builds to a max of 110-115psi.
I’m going to drive the car here and there but keep a close eye on things. Maybe do a very early oil change to check for signs of coolant in the oil again and to see how much metal is on the magnetic oil plug.