Fleetguard complet blue longlife antifreeze for Cummins ISL

Actually, you should not want our opinions.

This from Fleetguard's website:

http://www.cumminsfiltration.com/html/en/products/cooling/coolant/es_compleat/es_compleat.html

ES Compleat™

Use ES Compleat to provide superior engine protection, extend service intervals, and simplify your maintenance program.

DESCRIPTION

LITERATURE

REAL™ Performance

Lifetime coolant with service interval at 150,000 mi, 250 km, 4000 hrs
Provides antifreeze and antiboil protection
Best liner pitting and corrosion protection
Best aluminum and solder protection
Compatible with gaskets, elastomers and other non-metallics in the engine
Optimizes cooling system performance and water pump life
Contains proprietary scale inhibitors

REAL™ Versatility

Compatible with all other antifreeze/coolants
Choose from EG & PG formulations
Available in 50/50 & 60/40 premix
For all diesel, gasoline and natural gas engines

REAL™ Serviceability

Additive levels easily maintained via ES Extender liquid or a chemically charged filter
Easy to use test strips monitor glycol and additive levels providing protection against coolant dilution

Extend the life of your coolant
At 150,000 miles, refortify your coolant with ES Extender, a liquid chemical specifically designed to replace the additives depleted in the prior service interval.


End of Fleetguard quote.

Since you are unlikely to drive 150,000 miles in your RV you may not need to add anything.