The method is based on additive labelling using radiotracers, which are made representative of poisoning metals (i.e. zinc and calcium).  Oil or additive labelling does not require complex chemistry and results are provided on-line during engine operation.  The quantity of marker added to the oil (<1ml) or additive is such that lubricant properties remain unchanged.

3-D MAP OF ASH DEPOSITION The method is non-intrusive and it does not require the use of a special fuel. It makes it possible to study deposit profiles inside the catalyst (or particle filter) and to map ash deposits without opening the post-treatment device since measurements are performed through the canning (see picture).   Several radio-tracers can be used simultaneously for tracing different metals and the very high sensitivity of the new method allows quantifying extremely low levels of ash deposits in the range of micrograms, which typically corresponds to a few min. of engine operation.   SAE AWARD  This new method is fully described is SAE paper 2005-01-2178, which received a "SAE Award for Research on Automotive Lubricants". This paper is entitled "An Innovative On-Line Measurement Method for Studying the Impact of Lubricant Formulations on Poisoning and Clogging of After-Treatment Devices".  More info here