They dont 'Run better' on A5/B5 than A3/B4.
The euro 4 diesel onwards are better on A/B spec oils than C spec oils as contrary to popular belief and general wisdom, the full saps oils give less trouble with dpf's.
See here
https://www.volvoforums.org.uk/showthread.php?t=283503 for plenty of oil info based on nearly 10 years of studying facts, rather than the sheer amount of misinformation and misunderstanding found on general forums, facebook, etc.
In your case, you'd be as well using 0w40 A3/B4 though the shell will be fine, its an extremely light 5w40, I wouldnt recommend other 5w40 though unless you know your engine is very worn for sure.
The mileage is irrelevant.