Fuel saving and emission reduction are big challenges in the development of diesel engines. Diesel particulate filters (DPF) can effectively reduce particulate matter (PM) emissions of diesel engines but negatively affect the engine fuel economy. Some previous studies have been conducted to investigate the effects of DPFs on engine fuel economy, however, nearly all previous studies have neglected the impact of ash accumulation on DPF related fuel penalty. This work aims to quantitatively estimate the impact of ash accumulation on DPF related fuel penalty for a typical modern on-road heavy-duty diesel engine. For this purpose, a one-dimensional full-size DPF model considering ash effects was built and validated in this work, and an engine bench test was conducted to evaluate the effects of exhaust backpressure on engine fuel consumption. An estimation method for the quantitative evaluation of the impact of ash accumulation on DPF related engine fuel penalty was proposed based on the model and experimental data. Subsequently, the impact of ash accumulation on DPF lifetime fuel penalty as well as the potential of fuel saving by DPF ash management for a typical modern on-road heavy-duty diesel engine were quantitatively analyzed. In addition, the effects of engine-out PM emission concentration and DPF maximum soot loading prior to regeneration on the impact of ash accumulation on DPF lifetime fuel penalty and the fuel saving potential of DPF ash management are investigated with the estimation method. The results showed that the DPF ash induced fuel penalty ranged from 0.02% to 0.42% for the typical modern on-road heavy-duty diesel engine studied in this work, and the DPF lifetime fuel penalty could be reduced by optimizing the DPF ash cleaning interval. The fuel saving potential of DPF ash management ranged from 0.22% to 0.69% for all the cases studied in this work, which has the similar magnitude to some specific individual applications such as engine friction reduction, lowering accessory losses, or pumping optimization. Both the DPF ash induced fuel penalty and the fuel saving potential of DPF ash management are increasing with the rise of engine-out PM emission concentration no matter the DPF control strategy is implemented without or with ash correction, while the DPF maximum soot loading prior to regeneration showed little effects on the ash induced fuel penalty and the fuel saving potential of DPF ash management.