High potassium and sodium in oil sample
The last 4 oil samples I've had ran have shown high Potassium (40-44) and high sodium levels (108-95) but no Glycol. I do have to add a gallon of anti-freeze every few weeks mainly do to a few cold leaks. The engine is a 07 Cat C-15 with 900,000 miles. My mechanic says it could be anything from a bad head gasket to a leaky oil cooler. Any ideas on what I need to do now?
You have a coolant leak. A lot of the times the glycol doesn't show up. The potassium and sodium are classic signs of antifreeze in your oil.
You need to get in to the shop and find out where it is coming from. You have gone long enough with the coolant in the oil. Not sure which is the most likely cause but you need to find it ASAP before it does to much damage to the internal engine parts.