Nope......If you look at the pack, it should have a rating, the diesel starting with a Cxx and then /Sx - the C is the rating for compression engines, the S for spark ignition....
So what we need is the answer to the make of car and year - and the oil type - full title please, and if you can give us the grade like 5W50, that would help us determine the answers....Zac is right in an implication that most cars, unless very high end, are perfectly happy on a semi-syn.
Car is a Mitsubishi Mirage, 2013.
Oil recommended includes 5W40
Engine was topped up from min mark on dipstick to max with Halfords Fully synthetic diesel oil 5W/40 made to standard ACEA-A3, B4 and API-SM, CF
As its so new, I would recommend phoning a main dealer as anything which goes wrong could invalidate the warranty. As its the same grade you should be ok, but best to check. The service dept should be open on a Sat morning.
You should use the correct oil for your car not a cheap halfords one, if your car is still under warranty you could already have lost the rest of the warranty as servicing should be done at a vat registered garage where they would have signed the service book!
Toureman,
looking at the OP's information, the car has not had an oil change, but a top up from min to max on the dipstick. I am guessing this will involve no more than about one litre of oil, so only about 20% of the total oil volume will be "incorrect"
It should be all right with the SM specification......the warranty point is true but then if they do not offer to replace the oil as part of the service they can not insist on exclusivity, only reference it.