Original MGA oil filter elements were made of thick felt, which has the characteristic of trapping particles not only on the surface but also deeper within the fabric. While this has the ability to trap more dirt than a paper filter element before becoming clogged, it does not necessarily trap all of the smallest particles. The felt elements are good at holding large amounts of contaminants, such as may be encountered with very long oil change intervals. Also, in the era that these cars were built it was common to use non-detergent motor oil, which is not very good at holding contaminants in suspension, so a lot of sludge could settle out in the bottom of the sump. This required shorter oil change intervals, and if neglected had the ability to badly clog the filter. In that case the felt filter elements seem like a good idea. But keep in mind that when a filter does get clogged some (maybe most) of the oil can go through the bypass valve and not get filtered.

Replacement oil filter elements can still be purchased with the felt material. Otherwise there are also oil filters available constructed with paper filter media. In fact nearly every new spin-on type oil filter is constructed with the paper filter media, lending some credence to its integrity. So it should be no surprise that the use of paper type replaceable filter elements is also popular. The paper elements are less expensive than the felt elements, and the paper element has the ability to trap smaller particles, assuming it is properly constructed and properly maintained. The spin-on filters are readily available at most any auto parts stores, but the insert type filter elements may not be. Refer to the instructions supplied with the adapter to determine which spin-on filter is required.

As a note of individual importance, the spin-on filter adapters do not have a pressure relief bypass valve. As such, it is imperative that the spin-on filter itself must have a pressure relief valve built into it. Also the spin-on filter may or may not have an anti-drain back check valve. This is recognizable as a rubber flap that covers the perimeter holes in the filter at the attachment end. A filter used with the inverted adapter should have the anti-drain back valve. For the hanging filter installations the anti-drain back valve is not imperative, but may still be of some benefit to retaining oil in the engine block.

Filter descriptions, original MGA type - - Filter Descriptions, original variations
Filter Cartridges - - Filter Seal Rings - - Spin-on adapters, Aftermarket
Spin-on adapters, MGB - - Filter types - - Frequently asked questions
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