The common place to look is around the valve cover. At highway speeds the oil gets pumped up there faster, but it doesn't drain back any faster since gravity stays pretty much the same at any speed. :) Oil builds up on top and can overload the gasket.
Also at higher speeds there's more blowby past the piston rings. You're at the mileage where that starts to show up more. That blowby causes pressure to build up inside the engine faster than it can be drawn off by the PCV system. That pressure aids in pushing air past any less-than-perfect seal of a gasket, and when oil is building up there, it gets pushed out where it sits on the engine or runs down, often onto hot exhaust parts.
To identify this, you have to hop out right away; (don't wait five minutes), and see where the smoke is coming from. You may also see black staining on exhaust parts or what looks like hardened soot.
Another method is to add a small bottle of dark purple dye to the oil, then search a day or two later with a black light. The dye will show up as a bright yellow stain that you can follow back to the source. Auto parts stores will have the dye, and those that rent or borrow tools should have a black light.
An inexpensive attempt to solve this is to replace the PCV valve. If that gets plugged or partially blocked, it can't suck in the air from the bottom of the engine. That's when that blowby causes more pressure to build up inside, and oil will be more likely to get pushed out through a leak.
Monday, November 10th, 2014 AT 5:38 AM