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Which Filter Is Which?

Date: 3rd January, 2017


MAHLE has an abundance of technical knowledge in regards to filtration systems for all sorts of vehicles. It is this expertise that allows the company to recognise issues and assist technicians to overcome potential installation difficulties. A prime example, because of their similarity, is confusion over the MAHLE Original and Knecht Filter OX 404 and OX 813/1 filter elements.

The OX 404 caters for a wide range of vehicles, such as various models from BMW, Mini and Toyota, whereas the OX 813/1 is specifically for particular BMW applications. However, because the two filters are very similar in design and appearance, it can be difficult to distinguish which oil filter is which and this can lead to the wrong oil filter being inserted into the wrong housing.

This is a common mistake among workshop technicians, but a simple one to avoid when they know what to look for, as the difference between the two is a locating  tab that is visible on the inside of filter OX 813/1 (see image, below).

Media Library - Mahle Which is which

Design difference

Both filter inserts have a closure plug on the front end that MAHLE term a ‘pin’. When the insert is removed, this pin reveals a return bore in the filter housing so that all the oil from the module can drain into the oil sump. In turn, the pin in the new insert seals this return bore so that the oil circuit is again intact after assembly.

What can’t be seen between the two filter inserts is a design difference in the way the pin fits into the return bore during installation. The previous design allows the pin on the OX 404 to slide up to the return bore in the oil filter housing by means of a helical guide rail, called ‘the ramp’. In the new design, the pin on the OX 813/1 is fitted in the proper position by means of a locating tab on the inside of the filter.

If an attempt is mistakenly made to fit the OX 813/1 in a housing intended for the OX 404, the action is prevented by the locating tab on the inside of the filter. In the opposite case, the technician can’t detect the difference and is able to fully fit the insert in the module. However, although no blockage occurs, if this error goes unnoticed, the oil pump will be unable to build up oil pressure, resulting in severe engine damage.

It is therefore crucial that prior to installation, the technician checks the oil filter insert is the correct one for the housing and, where appropriate, the locating tab is visible inside the insert.

Which Filter Is Which?

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