todays oil

I run 10/60w full synthetic in my Commando, the furring I used to get on the sump magnet is no longer there at oil change time, and I run to extended oil change to offset some of the extra cost.

Been using 10/40 semi synthetic for years in my 850. If anything, the engine seems a bit livelier.

Once more unto the chestnut! Planning an overhaul of my Mk 2a this spring, re-bore, etc,etc, isn"t there something to the effect you have to run it in using mineral oil (not sure how long for) and then swop to synthetic, or is it semi-synthetic and its better if it was designed for an air cooled engine? And at one stroke, what should be simples gets ever more unsimples . Is therea consensus yet?

Yes you must use old dino oil to run the bike in before switching to Synthetics, you need the friction to bed the rings into the bore. I do it for 1500 miles before changing to Synthetics, I use cheap supermarket 20/50W and change it a lot.

Sorry to dig all this again but do mean cheap supermarket 20/50 synthetic as of 17" Jan,or do you mean the non-cheap 10/60 Harley stuff? which is on your post of 20" Jan . I"ve got to make a decision about all this soon and I need to get it right.

For running in non-synthetic 20/50W supermarket, once run in then full synthetic group 4 10/60W. The group 4 means its proper synthetic and not dino oil repackaged chemically just enough to be legally called synthetic but luckily never seen 10/60W that is not group 4.

If you are switching to a fully synthetic then make sure the motor is fully run in before switching . Also the mixture needs to be correct for clean running. Extending the oil change intervals with a dirty running condition will soon give problems.

5 litres of Morris V twin 20:50 is £31.87 it's a mineral oil and probably as good as a Commando needs. IMHO. Thats two oil changes and some to top up. I don't think a low performance air cooled engine warrants state of the art synthetic oil. I'm lucky to own a Triumph Street Triple that revs in excess of 13,000 rpm and runs pretty hot. A high performance engine with very close tolerances probably does justify a synthetic oil, though Triumph do include semi synthetic in their list of acceptable oils.

I go by the evidence of the magnet in my sump, it was always furred up on oil changes, after changing to synthetics it is clean on longer oil changes. So wide or narrow clearances the wear is less after changing to synthetics, it may be because its slippier or that it degrades less when it goes over the hot spot in the head next to the exhaust spot, no really bothered as long as the wear is less.