across dpf 20 can be calculated by controller 32 based on the difference in pressure measurements between sensors 34 and 36 controller 32 provides input to fuel supply system 16 which may cause engine 14 to change the exhaust temperature flowing through exhaust system 18 to dpf 20 causing a regeneration of dpf 20 now additionally referring to fig2 a and 2b there is shown an ash loading prediction method 100 utilized within controller 32 which may be interconnected to other sensors and control systems controller 32 may have other functions unrelated or indirectly related to the functions of method 100 of the present invention method 100 includes a step 102 in which the dpf service age u03c1 as well as the time between regenerations u03c8 are separately integrated by a process of integration or summing this summing of the dpf service age u03c1 and this step also keeps track of the time between regenerations u03c8 at step 104 a decision is made as to whether dpf 20 requires a regeneration this may be decided upon the delta pressure across dpf 20 as sensed by sensors 34 and 36 under the control of controller 32 and upon other portions of method 100 such as the compensation for the ash loading that is occurring in dpf 20 with the ash loading prediction being made by the present invention then the contribution of backpressure in dpf 20 that is attributed to the particulate matter.