Castrol Classic Greases & Fluids covers the chassis-lubrication, brake and clutch hydraulic, and cooling-system specifications that classic British cars were originally designed around. The principle is the same as the rest of the Castrol Classic range: classic chassis and hydraulic systems used a specific family of greases and fluids matched to period seal materials, period metals and period operating conditions, and substituting a modern multi-purpose product is not always the right call. The three product families covered here, greases, brake and clutch fluid, and coolant, each address a part of the routine service that is too often skipped or carried out with whatever is to hand on the workshop bench.
Greases
Classic chassis lubrication has more variety than a modern car: front-suspension swivels and trunnions on the MGB, MGA, Midget, MGC and contemporaneous classics need a dedicated king-pin grease pumped through three nipples per side at the recommended service interval; early steering boxes and rear axles on the pre-war and post-war range specify a semi-fluid grease the gun cannot pump in the usual way; propshaft sliding splines and universal joints need a lithium or moly-fortified grease that resists fling at speed; and graphite grease has its own niche applications across the range. Castrol Classic Greases cover each of these specifications in the correct chemistry.
Where the original handbook calls out a Castrol grade by name, and many MG, Mini and Triumph handbooks do, the modern equivalent in the Classic range is the direct replacement.
Clutch & Brake Fluid
DOT4 glycol-ether fluid is the correct specification for the brake and clutch hydraulic systems on the majority of the classic MG range, MGB, MGC, MGB GT V8, Midget 1275, MGA disc-brake cars and the wider classic British fleet from the late 1950s onwards. DOT4 is hygroscopic, meaning it absorbs atmospheric moisture over time, and absorbed water lowers the boiling point and promotes internal corrosion of cylinder bores and pistons. The right service interval is a full drain, bleed and refill every two years regardless of mileage, more often on cars stored in damp conditions. DOT5 silicone fluid is also stocked for concours and long-term storage applications, but it is not a drop-in replacement for DOT4, the two are chemically incompatible and must never be mixed, and DOT5 is not approved for motorsport or track day use.
For the full technical picture, see the dedicated Clutch & Brake Fluid material in the relevant per-model Brakes node.
Coolant
Classic engines run mixed-metal cooling systems with iron blocks, aluminium cylinder heads on later cars, brass radiators and copper-and-aluminium heater matrices, and the right coolant chemistry protects every metal in the system without sacrificing one for the others. Castrol Classic Coolant in the appropriate specification covers the standard road-use requirement; for the Forlife / 4Life classic-compatible long-life formulation developed specifically for the mixed-metal classic system, see the dedicated coolant range and the technical detail at 4lifecoolant.co.uk. The critical point applies regardless of brand: modern OAT (organic acid technology) long-life coolants must never be mixed with the traditional inorganic glycol coolants the classic systems were filled with from new, and mixing the two produces a gelatinous sludge that blocks the system.
If the coolant history of the car is unknown, the safe approach is a full flush and refill with a single known specification. The MGOC Spares technical team can advise on the correct grease, fluid or coolant grade for any specific car. For the full Castrol Classic product range and the Castrol Classic Oils Oil Finder, classicoils.co.uk is the authoritative reference.