Rick's Free Auto Repair Advice

Engine Block Heater

Engine Block Heater — which one is best for you?

What does a block heater do?

Cold metal quenches the combustion process and reduces fuel vaporization making it harder to start your engine in extremely cold weather. Quenching and reduced vaporization affects carbureted engines far more than fuel injected engines.  However, some early fuel injected engine also have trouble starting in extremely cold weather. An engine heater warms the coolant and the block, which reduces quenching and aids in fuel vaporization and starting.

Rick’s advice for the best block heater

I’ll show you the three types below. The most effective block heater is core plug heater because it’s in direct contact with the coolant surrounding the cylinders. Unfortunately, it’s also the most difficult to install on some engines.

If you’re going to install a core plug heater, also consider attaching a battery maintainer to your battery. That way you’ll have warm coolant and a fully charged battery.

What about oil pan heaters?

I think they’re a joke because they don’t heat the oil in the engine and that cold oil is what slows down cranking speed. The warm oil doesn’t start circulating until the engine is warmed up. And that’s only if the oil pan heater creates more heat than you lose due to heat loss from extreme cold surrounding the oil pan.

Magnetic oil pan heaters are also an issue is you have an aluminum oil pan or an oil pan with cooling flutes. Magnetic oil pan heaters don’t work in either of those cases.

Three types of engine block heaters

Engine block heaters come in three versions: lower radiator hose heater, tank heater, and core plug heater.

engine block heaters

Tank heater

A tank heater style block heater splices into a heater hose. It heats the coolant returning to the engine from the heater core and the heated coolant circulates through the engine by convection (there’s no pump involved). This type of block heater has fallen out of favor somewhat due to the use of metal heater tubes and the complexity of installation on late model engines.

Tank type heaters require a moderate amount of installation time and knowledge to locate the proper heater hose and install the unit and auxiliary hoses.

Lower radiator hose heater

A lower radiator hose heater splices into the lower radiator hose. The heated coolant rises directly into the engine.  To purchase a lower radiator hose heater, you must first know the inside diameter of your lower radiator hose.

Installation is fairly easy; just drain the radiator, cut the hose and clamp the heater in place

Core plug heater

This heater is the most difficult to install but is the most effective at heating the engine’s coolant. It installs directly into a cooling passage in the engine block in place of a factory core plug (sometimes incorrectly called a “freeze plug”). To install, drain the engine and remove an existing core plug. Then install the heater in to core opening and tighten. The heat goes directly into the engine to warm the metal.

Other types of engine heating devices

Magnetic oil pan heater

Magnetic oil pan heater

Kat’s 1155 200 Watt Magnetic Oil Pan Heater

This device attaches to the oil pan of your engine and heats the oil. The reasoning behind this type of heater is that cold oil slows the cranking speed of your engine. So warming the oil, in theory, allows it to crank faster and start up easier.

The theory falls apart a bit because the warmed oil isn’t in the engine, it’s sitting in the pan. And it won’t enter the engine until you start cranking. So it really can’t help your engine start faster. The only thing is does is help oil flow faster once the engine is running.

Do you need a magnetic oil pan heater? Probably not. Most modern vehicles use a 5W-30, 5W-20 or 0W-20 oil, all of which allow your engine to crank faster in cold weather. Also, many of these oil pan heaters don’t have enough wattage to heat the oil and overcome the heat loss on extremely cold days.

Heating blanket

A heating blanket can be used to warm the oil pan or heating blanketthe battery. Just like the magnetic oil pan heater above, a heating blanket can be used to warm the oil pan. I’m not a big fan of either of these devices because heating the oil doesn’t really help you start the engine and driving the vehicle heats the oil much faster than either of these devices.

Heating blanket for the battery

Lead acid batteries make power through a chemical reaction. The colder the weather, the slower the reaction. To get more power for starting, some people wrap a heating blanket around the battery. It works, but it’s not the most effective way to get the most power out of your battery in cold weather.

Rather than warming the battery with a heating blanket, I recommend using a plug-in battery maintainer. The maintainer will keep your battery at a full charge, eliminating the need for a warming blanket.

Use a battery maintainer

This is the most effective way to keep your battery fully charged to provide the fastest cranking power when starting on a cold day.

I receive a commission from Amazon if you order any of these products from these links.

PL2140 battery maintainer

Clore/Solar ProLogix PL2140 battery maintainer

©, 2021 Rick Muscoplat

Posted on by Rick Muscoplat

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