Had a look around the net etc. There is conflicting information about LRP and Unleaded. The fuel companies DO NOT recommend the use of LRP in cars with catalytic converters. The additive in LRP is potassium. I'm not sure if a different additive is used in Unleaded. The potassium maybe reacts with the cat ????
Another point is......LRP does not have to conform to any standards, so you might be putting crap in your tank.
Potassium (sodium can be used) has an affinity to water, which means there is a chance the fuel can become contaminated with water (by absorption from atmosphere etc.) more easily.
Here's a bit from Texacos site:
Texaco Lead Replacement Petrol (LRP)
Texaco LRP was introduced for use in petrol (spark Ignition) engined vehicles as a direct replacement for the now obsolete, 4* Leaded Petrol.
Texaco LRP has the same octane as the (now obsolete) 4* leaded grade and so no alterations to the ignition setting should be required. In addition LRP contains potassium based anti wear additive to help protect the engine from exhaust valve/seat wear.
LRP is recommended for use in vehicles which previously used 4* Leaded Petrol but is not recommended for vehicles fitted with a catalytic converter nor for continuous use in vehicles used for racing, towing or driving at high speeds for long periods of time.
In cases where such driving styles are required the vehicle manufacturer should be consulted as to a longer-term remedy, such as having hardened valve/seats fitted.
Texaco Lead Replacement Petrol contains a detergent additive to help keep carburettors, fuel injectors and inlet valves clean, maintaining driveability and performance.
Still no clear answers, but I would steer clear of LRP in modern engines.....just to be safe.