[10/10ths]

DUDE....If you are only firing her up and driving her 15 minutes at a time, you MUST change the oil every 6 months.

Your oil is not getting hot enough to burn out the impurities that accumulate from piston ring blow-by. Your rings don't get hot enough to completely seat the cylinder walls in fifteen minutes, so every time you drive that car for such a short period, you are loading the oil with exhaust contaminants.

These contaminants sit in the sump and acidify overnight as the air cools and condensation forms, leading to acid in the sump which is eating away at your engine right this minute. You are creating an acidic fluid that is inside your sump and eating every bit of metal like a cancer. You need to drive her for at least thirty minutes at a time once a week and burn that stuff outta there.

And change your oil every six months.

Oil is cheap.

H6 engines are expensive.

Brown bag it if you have to.

Good luck.