Posts Tagged: motor oil sludge buildup

Why Engine Oil Turns Into Sludge and Varnish

What Causes Engine Sludge and Varnish? Quick Summary Motor oil doesn’t “just get dirty.” Over time, heat, oxygen, fuel dilution, moisture, and combustion byproducts chemically break it down. That breakdown creates oxidation byproducts that thicken into varnish and eventually harden into engine sludge. • Engine sludge and varnish are caused by oil breakdown, contamination, and heat. • The #1 root cause is oil oxidation combined with extended oil change intervals. • Sludge is a soft, thick deposit; varnish is a hard, baked-on coating that sticks to engine parts. • Low-quality … Read More