This section covers engine oil specification, oil filtration components, oil cooler ancillaries, and engine paint for period-correct restoration. The oil specification, filter type, and engine colour all varied across the Midget's production life, and using the correct specification is important for both engine longevity and authentic restoration.
Engine Oil
A quality 20W/50 mineral oil is the recommended lubricant for all Midget engines. Castrol Classic XL 20W/50 is the standard recommendation, formulated specifically for classic engines with the zinc and phosphorus additives (ZDDP) that flat-tappet camshafts require for adequate wear protection. The ZDDP content is critical, modern low-viscosity oils designed for fuel economy in contemporary engines have reduced ZDDP levels to protect catalytic converters, but this makes them unsuitable for the Midget's A-Series or Triumph cam and follower surfaces. Running a Midget engine on modern low-ZDDP oil will lead to accelerated camshaft lobe and follower wear.
Engine Oil Capacity
The engine oil capacity differs between the 1275cc and 1500cc, and is further increased if an oil cooler is fitted. When an oil cooler has been newly installed, the sump must be topped up to account for the additional oil held in the cooler circuit, typically over a pint.
However, when subsequently draining the engine for an oil change, the old oil in the cooler circuit will remain unless the hoses and cooler are removed and emptied separately. The quantity of fresh oil needed for a routine oil change is therefore the same whether or not a cooler is fitted.
Oil Filtration
Three distinct oil filtration systems were used across the 1275cc range, each requiring its own filter type. The earliest 1275cc engines used the original bowl-type paper element filter.
This is a canister with a removable bowl, a paper element, a pressure plate with seals, and a centre bolt. The bowl must be carefully reassembled with the seals correctly seated to prevent oil leaks.
Oil Filtration Changes
From a specific point in 1275cc production, a spin-on canister filter was adopted. This is a much simpler arrangement that screws directly onto a filter head bolted to the block. A second change later in production introduced a revised filter head and adaptor with a different spin-on filter.
Spin-On Conversion
A spin-on conversion kit is available for owners wishing to upgrade early engines from the bowl-type assembly. This replaces the entire filter head and bowl with a modern spin-on adaptor, providing easier servicing with widely available filters. The conversion bolts to the original mounting points.
1500 Oil Filtration
The 1500 uses its own spin-on filter arrangement from the outset, with a filter head and adaptor specific to the Triumph engine block.
Oil Thermostat and Oil Cooler
An oil thermostat (oil stat) can be fitted in conjunction with an oil cooler to regulate oil temperature and prevent overcooling in cold weather. The oil stat sits in the oil cooler circuit and diverts oil away from the cooler until the oil reaches operating temperature, at which point it opens to allow oil to flow through the cooler. This prevents the engine from running with excessively cold oil, which is almost as harmful as overheating, cold oil is too viscous to circulate effectively through the bearing clearances, and its lubricating properties are reduced.
Engine Paint Colours
Period-correct engine paint is available in aerosol cans for restoration. The Midget engine colour changed across production: MOWOG green (also called BMC engine green) on the 12CC 1275cc engines used in 1967, light green hammer finish on the 12CE engines from December 1967 through 1971, and black on the 12V-prefix engines from 1972 onward and on all 1500 Triumph engines. Getting the engine colour right is a detail that distinguishes a well-researched restoration from a generic respray. MGC green is also stocked for owners restoring other classic MG variants.
Primer and undercoat are available for a complete refinish.