How Does a Diesel Engine Block Heater Work?

by Derek Odom


Normally, block heaters are installed in one of the factory freeze-plug locations. This allows them to most effectively heat both the coolant and the oil at the same time. They run off normal house 110V AC outlets, and many times the plug for the block heater can be seen hanging out of the grille. These heaters are popular in the Midwest, where winter temperatures regularly dip low enough to freeze the fluids in a vehicle's engine. It is recommended to have a qualified shop install your block heater, but if you're an experienced do-it-yourselfer who knows your way around an engine compartment, you shouldn't run into too many problems.

Time Frame

Typically, people plug their engine block heaters in before bed and let them run until the morning, when they have to start the vehicles again. Studies have shown, however, that four hours of block-heating time is optimal and very little good is done after that point. Therefore, you can conserve power and save money by not having your engine block heaters going for eight hours at a time. A standard timer switch can be implemented to aid this process.


Cold oil and coolant is thick and viscous, and it is difficult for the engine to circulate such fluids. A block warmer keeps these components at a higher temperature, which makes the car start and run better in the morning. It also helps the engine reach operating temperature much faster, which improves power and economy, allows the heater inside the passenger compartment to be more effective, and provides proper lubrication to the engine and all its parts.


Some companies offer heating blankets that span the entire engine bay and keep everything warmer on cold nights. Some people recommend battery warmers, which keeps only the battery warm but aids in cold starting power. Aftermarket heaters that temporarily attach to the oil pan are used to heat the oil, giving better lubrication during cold starts.

More Articles

article divider