Thank you to everyone for your replies.
My understanding was based on what the technician at the dealer I bought my 650 from in 2015 and the ‘how to check the oil level’ from the owners manual, which is the same in the 650 and 1050 manuals.
As I was buying my 650 I was told that for 2015, Suzuki had altered their recommendation for oil from semi-synthetic 10/40 to fully synthetic 10/40 and doubled the service mileage from 3750 to 7500, purely because of this change. The Orwell’s technician recommended to keep using semi-synthetic and do an oil change at the old 3750 limit between the 7500 services. He said it was something to do with the 650 clutch working better on the semi-synthetic oil.
I did this throughout the 40,000 miles I had that bike for and never had a problem and think I had to top up between those changes only once.
When I changed the oil I did the 3 minute run/3 minute drain down procedure from the manual and this seemed to work fine. But this was whilst filling from empty, so that might have simplified things.
When I bought my 1050 I saw the service limits were 7500mile so assumed that would mean fully synthetic oil required. This was from a different dealer and I didn’t think at the time to check.
I was surprised when I rang them last week, to check what they had used at the 600 mile service before I topped it up, to hear it was semi synthetic. The bloke I spoke to said Suzuki recommended both semi-synthetic and fully synthetic 10/40 oil for the 1050, both with an oil change limit of 7500 miles. He said it was purely down to personal preference so long as the two different types weren’t mixed. I knew they couldn’t be mixed, which had prompted my call to find out what they had used.
I’m hoping to clean all the chain lube/ Scottoiler oil (result of being a total numpty
) off the bike in the next couple of days and then give it a run with the oiler turned off. Hopefully this will show no signs of any leak and I can carry on enjoying my ownership of this great bike.
Thank you again for sharing your advice with me.