I had to laugh when I saw the thread topic (oil for a 2L TS Selespeed) - in mine, the important thing is that it actually HAS oil
The day I bought the car, on the journey home (>1000km) I didn't think to re-check the oil (I'm sure I checked it at the start) - by the time I got home, no oil showed on the dipstick
First I changed the oil - used Castrol Magnatec, 10W40, no worries.
Then I found it needed topping-up barely a week later! (My other cars, which are old and Italian, never require top-ups between changes).
Over the next month or two, I managed to use up all the leftovers I had of 10W40 (from various other oil changes), then I used up the leftovers of 15W50, then some 10W60 that I use in my Uno Turbo, and now finally I'm having to actually buy oil just to top up the 156. I'm now using a budget 20W40 oil, the kind you would buy from a supermarket. It would not normally be my choice but on an engine that uses oil very quickly, I question the need for a high-quality oil. And I feel that in the summertime, thicker is better.
I hope to pull my engine apart within the next couple of months and solve this consumption problem - it uses 1 litre every 800km. I think TS stands for 'Two Stroke'...
As for 'wankski' (what a name!
) - I see that you're not fond of cambelts
Cam chains have their problems too (chains stretch, sprocket teeth wear) and in some ways it's nice to restore all parts of the drive system to new-condition when you replace the belt, tensioner, and idler. With a cam chain, you would have to replace all sprockets, slipper blocks, and chain to get it back as-new, which is messier and more expensive. Plus the installation is more prone to oil leaks.
Comparing early cambelts (such as the 12V V6) to the one on the Twinspark, you can see that the newer cambelt is wider, thicker, and has rounded tooth shapes. That really ought to make it much more resistant to breakage and I personally think that's why Alfa Romeo extended the service interval to 72,000 miles. However, I guess the tensioner/idler became the new failure mode, and hence the return to 36,000 mile change intervals.