Which of the following describes a consequence of not cleaning the diesel particulate filter?

• A. Increased top speed
• B. Loss of power
• C. No engine issues
• D. Cleaner exhaust

Answer: (B)

Not cleaning a diesel particulate filter leads to soot building up in the filter, which makes the exhaust path through the engine more restricted. That increased backpressure means the engine has to work harder to push exhaust out, so the engine can’t breathe as well and loses torque. The result is slower acceleration and reduced ability to sustain high speeds, especially under load—this is the loss of power you’d notice in an emergency vehicle during rapid response or when climbing hills.

A clogged filter wouldn’t improve speed or make exhaust cleaner, and it’s not accurate to say there would be no engine issues; the buildup can trigger warning lights and even force the vehicle into a protective limp mode to prevent damage, further reducing power.