Lucas's marketing machine is kicked in as usual..
the lucas UCL is just that, a lightweight machine oil with very little (if any) detergent.
According the MSDS on lucas's UCL is't 10% addtive and 90% heavy paraffinic distillate, which is mainly lubricating oils and parrafin wax.
You'd have to run A LOT of the UCL to get it to clean anything.
The Regane is your best bet if you have to choose.
the lucas UCL has its place, but not 100% for what it's advertised.