So I took the 126 to another trip from LA to SF and back. Last time I did this, I noticed a couple of times when the car billowed blue oil-smoke for short periods.

On the way to SF, not a single problem. It ran like a top and I arrived to my destination smoothly. Drove it on I-5 for about 300 miles at an average speed of 80mph. Fuel consumption was around 19mpg.

On the way back to L.A., it had about 5 to 6 20-30second episodes where thick blue smoke billowed out. These were short isolated moments where the car just spewed blue smoke uncontrollably. The engine sounded fine when it happened and no systems seemed to run any worse for it. These episodes happened during steady cruising at around 75-80mph. Not during any acceleration or up any hills or during anything particulary strenuous. The smoking would stop as quickly as it started and the car would run fine until the next randomly designated time to smoke.

I did notice the smoking got thicker when I let off the gas.

The car does not emit any smoke at startup, during daily cruising around the city, and does not drive strangely. There are no dripping fluids on the ground. The smoking does not happen all the time. These appear to be little isolated episodes that I can't seem to attach to anything in particular... it just happens for a little while and it sucks while it happens, but then it stops.

Anyone have an idea as to what's wrong? Is this the engine being worn?

I maintain the car as well as I know how to - monitoring oil level, oil/filter changes every 3K miles, everything else is up to date. I always use Castrol GTX 20W50.

Is it time to switch to Synthetic? Is this just a stopgap measure? Is a motor rebuild/replacement the only option left? Does this sound like a top end issue (worn valve stems/guides?) or a bottom end issue (worn piston rings). I just don't understand why it doesn't ALWAYS or at least, often, smoke.

The car has 196,000 original miles. I've owned it since it had 150,000.

Thanks.