Fuel, Cost & Efficiency · Driver Training VideoIdle Reduction & APUs

Start with the money

A sleeper truck idling all night to run the heater or the air conditioner burns roughly eight-tenths of a gallon of diesel every hour it sits there covering zero miles.

It's hard on the engine too.

Now the regulation side

There's no single federal idling-time law, but most states and plenty of cities enforce their own limits — commonly five minutes — with exceptions built in for genuinely dangerous heat or cold, queuing at a dock, or running power equipment for a job function.

Here's the part that surprises drivers: the federal government actually builds in an incentive to idle less.

An APU itself is simple: a small unit, diesel-fired or battery-electric, that heats, cools, and powers the cab without turning over the main engine. It burns a fraction of what the truck engine does at idle, and it's quiet enough to actually sleep through.

Your company standard: if you're parked more than five minutes and it isn't a safety or power-equipment situation, shut the main engine down and run the APU instead. Know where local idling limits apply, and keep your APU documentation in the cab where an inspector can find it.

Less idling means a lower fuel bill, a healthier engine, and one less thing an inspector can write you up for.