MG MGB maintenance: the schedule, the costs, the traps
A 2-seat convertible roadster with a gas powertrain. Below: the service intervals with real cost ranges, the repairs MGB owners actually report, and when a fleet operator would sell. Same data Carlyle uses to score fleet buys.
Service schedule
What it needs, and what that runs
| Interval | Service | Typical cost |
|---|---|---|
| 3,000 mi / 3 mo | Engine oil & filter change (20W-50 mineral or high-ZDDP for the flat-tappet cam); grease front kingpins/swivel pins, propshaft, steering rack and water-pump nipples; top up carburetor dashpot dampers; check tire pressures, coolant/brake/clutch fluid levels, battery. Basis: factory 3,000-mi routine s | $90-$180 |
| 6,000 mi / 6 mo | Above, plus check/adjust valve clearances, clean/gap or replace spark plugs, inspect/replace contact-breaker points and set ignition timing, adjust carburetor idle & mixture (Zenith-Stromberg), inspect brakes, check gearbox and rear-axle oil levels, check fan/drive belt tension. | $220-$450 |
| 12,000 mi | Above, plus replace air filter element, fuel filter, spark plugs, points & condenser, distributor cap & rotor; check/repack front wheel bearings; full brake inspection; inspect clutch & brake hydraulics; check crankcase breather/PCV; assess coolant condition. Many owners fit electronic ignition here | $400-$750 |
| 24,000 mi | Coolant drain/flush & refill, brake fluid replacement, gearbox and differential oil change, wheel-bearing repack, top up/replace lever-arm damper oil, inspect suspension bushes and (age-critical) rubber fuel lines, brake hoses and coolant hoses. | $450-$900 |
Known repair windows
What MGB owners actually run into
Mileage ranges where these repairs typically show up. Buying above a window is not automatically a pass - it just needs to be priced in.
Structural body rust (sills/rocker panels, floor pans, wheel arches, front wings, battery boxes)
high severityAny mileage · $1,500-$15,000+
The defining MGB problem. Sills are the primary structural member; corrosion there or at damper/spring mounts compromises safety and can dwarf the car's value. Dry-climate or restored cars are far safer buys.
Lever-arm dampers (shock absorbers, front & rear) leak/wear out
medium severityAny mileage · $200-$500
MGB uses lever-arm dampers all round instead of telescopic units; they lose oil and go soft with age, degrading handling. Reconditioned/replacement units are cheap and widely available.
Kingpin / front swivel-pin wear
medium severityAny mileage · $400-$900
Front suspension trunnions/kingpins depend on the 3,000-mi grease-nipple lubrication; skipped greasing causes rapid wear, play, and knocking. A known consequence of deferred classic maintenance.
Cooling system silting / water pump / overheating leading to head gasket
high severityAny mileage · $250-$1,200
Neglected coolant lets the block/radiator silt up; chronic overheating on the 1.8L B-series can blow the head gasket. Water pump and radiator are typical wear items; HG job is the costly end of the range.
Carburetor wear (Zenith-Stromberg on 1980 US spec; SU on earlier)
medium severityAny mileage · $250-$600
Worn throttle shafts, perished diaphragm and gummed jets cause rough idle and poor running. Rebuild kits inexpensive; the 1980 car's single emissions-strangled Zenith-Stromberg is often the biggest driveability weak point.
Chronic oil leaks (rear main seal, tappet cover, front/rear crank)
medium severityAny mileage · $150-$1,400
B-series engines seep oil by design; the rear main (scroll-type on early, lip seal on 18V) is the worst and requires gearbox/engine removal, hence the high end of the range.
Clutch hydraulics (master & slave cylinders) failure
medium severityAny mileage · $200-$500
Rubber seals in the hydraulic master/slave cylinders swell and leak with age, causing loss of clutch actuation. Common age item; parts cheap.
Lucas electrical faults & SU fuel-pump points failure
medium severityAny mileage · $150-$400
Loose/corroded connectors, tired generator or alternator, and the points-type SU fuel pump sticking are classic 'Prince of Darkness' gremlins. Fuel pump replacement/points cleaning is a frequent roadside fix.
Gearbox 2nd-gear synchro wear / overdrive faults
medium severityAny mileage · $900-$2,500
Worn synchros (notably 2nd) cause crunching; optional overdrive units can fail electrically or hydraulically. Rebuild or exchange gearbox is the fix on high-mileage cars.
Operator notes
1980 MGB is the final production year (1962-1980); powertrain is the 1.8L (1798cc) 18V five-main-bearing B-series inline-four, gas, single Zenith-Stromberg carb on US emissions-strangled spec. Timing is a CHAIN, not a belt (no replacement interval, but tensioner/chain rattle appears ~60k-100k mi, ~$300-$700). Schedule basis is the factory Driver's Handbook/workshop manual: ~3,000-mi conventional 20W-50 mineral oil (or high-ZDDP additive for the flat-tappet cam), 6,000-mi interim and 12,000-mi full services; front kingpins greased every 3,000 mi. 1980 cars are negative-earth (pre-1967 were posi
When the smart money sells
On fleet math, a gas MGB retires around 95,000 miles. Carlyle's garage tracks this per car, against your actual odometer.
Cost ranges are typical US independent-shop estimates and vary by region and condition. Modeling, not mechanic advice - always confirm against your car's service records.
Thinking about buying a MGB?
Carlyle scores the exact listing - price vs. useful miles left, projected Turo income in your market, and a straight buy-or-pass call.
Find my car - freeFree chat every day. No credit card to start.