MGB Maintenance: Keeping a Classic MG on the Road

Written by Petro Olekhnovych, mobile mechanic in Aylesham, Kent

Good MGB maintenance comes down to little and often. Change the oil more often than you would on a modern car, using a classic 20W-50, and grease the front suspension swivel pins regularly. Keep the SU carburettor dampers and lever-arm shock absorbers topped up, and check the sills and floors for rust.

Know your MGB

The MGB was built from 1962 to 1980, as a roadster and later as the MGB GT coupé. It uses the 1,798cc B-Series engine, which switched to a five-bearing crankshaft in October 1964.

One detail catches people out. Early cars were positive earth, and the change to negative earth came with the Mk II in 1968. If you are connecting a battery charger or fitting any electrical accessory, check which way your car is wired first.

Your workshop manual or original handbook is the best guide to your exact car, so keep one handy.

Oil: the right type, changed often

The MG Owners’ Club Spares recommends 20W-50 multigrade for MGB engines, calling it the modern equivalent of the original handbook recommendation. It explains that these engines have wider bearing clearances than modern engines, which a thin modern oil does not suit.

It also stresses zinc (ZDDP). The B-Series uses flat tappets, and ZDDP protects the cam lobes and followers, especially on cold starts. Many modern oils have less of it, which can wear the camshaft over time. Look for an oil sold as suitable for classic flat tappet engines.

MGOC Spares suggests changing the oil every 3,000 miles or once a year, whichever comes first. If your MGB covers few miles, go by time. Moisture and acids build up in the oil even when the car is parked.

While you are at it, keep an eye on the oil pressure gauge. The Classics World buyer’s guide says it should show at least 40psi at 40mph in top gear. If the pressure drops sharply or the gauge falls to zero, stop the engine and get it checked.

Grease the swivel pins

This is the job MGB owners most often forget. The front swivel pins (also called king pins) have grease nipples that need regular attention.

Advice on how often varies. An Enjoying MG article by Richard Ladds says to grease the front suspension at every 6,000-mile service, or at least every six months. The Classics World guide suggests roughly every 3,000 miles. If in doubt, do it more often.

Why it matters:

• The Enjoying MG article says king pin or swivel pin wear is a common cause of MOT failure for MGs, most often due to lack of maintenance.
• The MG Car Club’s V8 Register warns that skipping it can lead to heavy steering, stiff suspension and eventually mechanical failure.
• Even when well looked after, Classics World says the king pins rarely last more than 50,000 miles.

The Enjoying MG article recommends a lithium-based grease and warns against graphited grease on king pins. Pump until fresh grease pushes the old out, then wipe off the excess. The handbrake cable has a grease point too.

Steering racks differ by age. Moss Motoring says early MGBs have a nipple on the rack housing that takes 90 EP gear oil every 12,000 miles or 12 months. Later racks have no nipple and are usually only lubricated when the gaiters are replaced. Moss warns not to fill the gaiters full of oil.

SU carburettor dampers

Each SU carburettor has a small damper on top that works in a column of oil. The V8 Register advises topping it up with engine oil, preferably 20W-50, until the level is just visible where the inside of the tube changes diameter.

If the oil runs low, the carburettor piston can flutter. The V8 Register says this hurts throttle response and acceleration. It is a two-minute check, so do it at every oil change. If the car still runs poorly after that, our guide to carburettor tuning explains the next steps.

Dampers, gearbox and brakes

Lever-arm dampers. The MGB uses lever-arm shock absorbers that hold their own oil. The Classics World guide says to check their fluid level and condition, along with the suspension bushes and shackles. Leaking dampers are worth sorting before they run dry.

Gearbox oil. Classics World says overdrive gearboxes take a multigrade oil and non-overdrive boxes take EP90. Check which box you have before topping up.

Brakes. Keep the brake fluid clean and at the right level. Classics World advises checking the rear wheel cylinders for leaks, especially on little-used cars. A spongy pedal, or one you have to pump, can point to worn master cylinder seals. If the brakes feel wrong, do not drive the car until they have been checked.

Rust: check before it spreads

On an MGB, rust is not just cosmetic. Classics World points out that the sills provide much of the body’s strength, even on the GT. Places to check:

• the sills, and where the floor meets the inner sill
• the sill drain holes, which can block with mud
• the inner wings and footwells, which have flat tops that collect water
• the bottom rear corners of the front wings
• the bottoms of the doors

Washing mud out of the underside and keeping drain holes clear helps. If the car is laid up for winter, our classic car winter storage guide covers how to do it properly.

How we can help

We are a mobile mechanic based in Aylesham, and classic car servicing and repair is a big part of what we do. We come to you across Canterbury, Dover, Deal, Sandwich, Folkestone, Wingham, Ash and the villages in between.

We can service your MGB on your driveway and carry out fault finding when something is not right. For bigger jobs, we also do classic engine rebuilds in our Kent workshop, and recommissioning for cars that have been off the road. If you have worn suspension or a steering fault, we can come out, diagnose the cause and tell you what it needs.

Labour is £30-£50 per hour depending on the job, and parts are extra. We agree the price with you on WhatsApp before any work starts.

Frequently asked questions

How often should an MGB be serviced?
Little and often. MGOC Spares suggests an oil change every 3,000 miles or yearly, and swivel pin greasing advice ranges from every 3,000 to 6,000 miles. Your handbook gives the full schedule.

Can I use modern oil in my MGB?
MGOC Spares recommends a classic 20W-50 with enough zinc (ZDDP) for the flat tappet engine, rather than a thin modern oil.

Does my MGB need an MOT?
It depends on its age and condition. Our guide to historic vehicle MOT exemption explains the rules.

Is my MGB positive or negative earth?
Early cars were positive earth. The change to negative earth came with the Mk II in 1968. Check before connecting anything electrical.

Need help? Send a WhatsApp to 07563 350335 with your car’s make and model and we’ll come to you.

Sources

• MG MGB (Wikipedia)
• Classic engine oils (MG Owners’ Club Spares)
• MGB GT buyer’s guide (Classics World, January 2026)
• Basic maintenance: greasing the front suspension, Richard Ladds, Enjoying MG (via MG Experience)
• Timely note: grease up those nipples (MG Car Club V8 Register)
• Carburettor dampers (MG Car Club V8 Register)
• Under the Bonnet: Steering System Lubrication (Moss Motoring)