The Ultimate Guide to Tractor Block Heaters

Living on a homestead in a locale that has cold winters means dealing with machinery not wanting to start when you really need it. So many of us rely on our tractors for snow removal that it’s absolutely necessary to ensure our equipment starts even when it’s bitter cold outside or even inside the unheated barn.

The easiest way to make sure our tractors will start is to keep the engine warm. Block heaters heat the engine block, oil pan, coolant system, or some combination of those so there is less wear on the engine as it’s turning over and allowing it to start quicker before running down your battery.

I’ll be talking temperatures quite a bit in this article and even though my middle school teachers guaranteed we’d be using the metric system in the USA by 1990, it still hasn’t happened yet. Therefore Fahrenheit is the only scale I’m familiar with and all temps listed are in Fahrenheit. For an easy conversion calculator check this website.

When Are Block Heaters Necessary

There are several factors that will go into the decision to install a block heater on your tractor or not. Some considerations are: age of the tractor, gasoline or diesel, synthetic or conventional oil, and whether it’s stored indoors or outdoors.

Generally, older gasoline tractors will be fine starting in the same temperature your gasoline vehicle starts at. These older tractors are generally carbureted and run on conventional oil. As long as the choke on the carburetor is working properly the engine shouldn’t have too much trouble down to about 0 degrees.

That’s not to say though that a block heater on one of these older tractors isn’t helpful. An engine heater can keep the engine oil at a viscosity that will get it flowing quicker to reduce the wear on the internal engine components.

Other than some garden tractors and riding mowers, nearly all tractors manufactured nowadays have diesel engines. Diesel engines can be more cold-blooded than gasoline engines.

Synthetic oils designed for colder climates have a more consistent viscosity even when the temperatures get bitter cold. This makes for easier turning over of the engine, quicker oil flow, and less wear on the internal components.

Engine Block Heater Ambient Temperature Chart

30° FNot Needed Not Needed
20° F Not Needed Useful
10° F UsefulUseful
0° F UsefulNecessary
-10° F or lessNecessaryNecessary

How Do Block Heaters Work

Essentially block heaters are nothing more than an electric heating element similar to the element in a water heater tank or an electric blanket. There are some types that run on a fuel source, but for this discussion we’ll just concentrate on the electric type.

To be technically correct, we should first define that an engine block heater directly heats the engine block of the tractor or vehicle. Most engine heaters will heat the oil or coolant that then transfers that heat into the engine block. Generally people will refer to any type of engine heater as a block heater.

Types of Block Heaters for Tractors

Magnetic Block Heater

Magnetic block heaters have a strong magnet built into the housing of the heater to temporarily affix it to the engine. These magnetic block heater are typically used to warm the oil by sticking it to the bottom of the oil pan, but they could be used to warm the engine block directly by finding a place on the engine that the heater will fit so it is fully in contact with the casting and not too close to a wire or fuel line that could melt.

Affixing the magnetic block heater to the engine block casting itself may not be worthwhile unless it’s near a location where coolant is located in the engine. This way the heat will warm the coolant to transfer the heat to the surrounding areas. A cut-a-way drawing of your tractor’s engine could help find a suitable location.

Normally magnetic block heaters are removed after the tractor is started so they don’t fall off somewhere in a snowbank lost until spring. One attached to the engine block casting could be left in place if you feel confident it would fall off. This way it’s easy to just plug it in when needed.

Magnetic block heaters come in several different wattage ratings for different applications or engine sizes. The nice advantage of a magnetic block heater is you can use it on multiple pieces of equipment as needed. I have a 200 watt unit that I use for my small Bolens diesel tractor. Here’s a video from my YouTube channel from the first time I used it on a bitter cold winter day:

Cold Diesel Start – Magnetic Block Heater Review

Blanket Heater

Blanket engine heaters are very similar to an electric blanket you’d use for yourself on your bed except a bit more heavy duty. These blanket heaters are better suited for use on top of a car’s engine compartment in my opinion. They would be more difficult to get into position on a tractor so that the heat gets transferred where it needs to go.

More specialized industrial applications and bigger machinery that has specially size and rated blankets are the more practical application for electric blanket heaters.

A non-heated insulated or moving blanket is useful though to drape over the hood of a tractor to help keep heat from another source trapped in the engine compartment better.

Silicone Pad Heater

Silicone pad heaters stick onto the oil pan of the tractor to warm the engine oil. They come in different sizes for different size engines and operate similar to a magnetic heater only these pad heaters are glued in place to allow you to just plug in the cord when needed.

The advantage to the silicone pad heater is it’s always in place when you need it and you don’t have to lay on the ground while attaching a magnetic block heater. The disadvantage is if you have multiple pieces of equipment that might need a block heater the silicone pad is not transferable.

Dipstick Heater

A dipstick heater replaces your oil dipstick with a long rod with an electric heating element on the end. The end of heater is immersed right into your engine oil. At first glance this type of engine heater might seem really simple and easy and can be bought for less than $20, but there are many stories of engines catching fire from these dipstick heaters and Canada has banned the sale of them due to engine fires.

Yesterday’s Tractor does sell a dipstick heater and there are many people that find them useful, but myself I’m going to stick to the magnetic block heater when I need quick attach easy to use block heater.

Coolant Heaters

Coolant heaters come in several different types:

Freeze Plug Heater

A freeze plug or frost plug heater is mounted in one of the holes in the engine block where the freeze plugs are installed. A freeze plug is a sacrificial disk that will break and push out in case of the water or coolant in an engine freezes. Because liquid expands when it freezes the freeze plugs are used to protect the engine block from cracking during a freeze.

A freeze plug is removed and the heater inserted in it’s place. The heater has a small heating element that keeps the engine coolant warm. Freeze plug heaters are generally lower wattage so they will need to operate for a longer period of time to warm the engine before starting.

Another consideration to using a freeze plug heater is getting the old freeze plug out can sometimes be challenging and as well as keeping the heater from leaking once it’s installed. Once the old plug is out be sure to clean the holes inner surface to allow for a tight seal of the new freeze plug heater. Freeze plug heaters generally have a removable cord.

Block Mounted

A block mounted coolant heater is threaded into a hole directly into the water jacket of the engine. To install one of these, a plug is removed and the new heater would be inserted into the hole. Using a high-quality Teflon tape will help to seal the threads to avoid leaks.

Lower Radiator Hose Heater

This type of coolant heater is mounted in line with the lower radiator hose of the engine. As the lower radiator hose heater begins heating the coolant in the hose, the difference in temperature will cause the coolant to slowly circulate through the system.

The hottest coolant will still be concentrated in the lower radiator hose, with temperatures decreasing in the farther reaches of the coolant system. These heaters are usually a higher wattage than a freeze plug heater, and could be easier to install in most cases.

Circulating Tank Heater

Circulating tank coolant heaters are an external heater and circulating pump that is ported into two opposite sides of the engine. The style of heater heats the coolant and circulates it through the engine to ensure the entire engine block and components are warmed and ready for startup. A thermostat can also be mounted in the engine block to control the heater so it’s not constantly on.

In my days as a maintenance electrician, I’ve installed many circulating tank heaters on backup generators for central dispatch towers and sewage pump stations. I mostly used HotStart brand heaters to ensure that our units were ready to run when needed.

What Size Block Heater for My Tractor?

Engine block heaters range from about 200 watts for magnetic and dipstick types to over 2000 watts for large permanent mounted coolant heater types. Choosing the right size block heater for your tractor will depend on several factors:

  • Size of the engine
  • Typical low temperatures of your region
  • Conventional or synthetic oil
  • Constant use or occasional use

Larger HP engines will have more mass to them and require more energy to warm them up. For example, I use a 200 watt magnetic heater on my 15 HP Bolens, Dad’s JD 2025R takes a 400 watt immersion heater and our neighbor’s 45 HP tractor uses a 600 watt coolant heater.

Here in Michigan where we live the nighttime lows typically get down into the teens or single digits so our heater selection is based on those temps. Different regions have their typical lows and places such as Minnesota or most of Canada might need to increase the size of their engine block heaters compared to places in the lower latitudes that have more moderate temps.

Using synthetic oil makes for easier starting of a diesel engine in those cold temperature too. Synthetic oil has less drag as the engine is turning over compared with conventional oil. This factor could also play a role in sizing your block heater.

How often a tractor gets used will be factor to consider when sizing your heater in addition to how much advance notice you’ll need before starting the engine. A tractor that gets used frequently and is plugged in after every use may need a smaller heater compare to the tractor that needs to heat up quickly because it’s needed for an emergent job.

My Bolens is only used in the winter to plow snow so I’ll use the weatherman’s snowfall and temperature forecast to help me plan when to plug my heater in. This give plenty of time for the little 200 watt heater to do it’s thing. Having a shorter period before start up would mean sizing the block heater somewhat larger to warm up the engine block quicker.

How Long Should I Leave My Block Heater Plugged In?

Leaving your engine block heater plugged in all the time or just before use is a matter of personal preference, but here a few things to consider:

  • A high wattage oil pan heater could “cook” the oil which degrades and shortens it’s life.
  • If an engine only requires a few hours to warm up than anything beyond that is wasted energy.
  • Constant use of the block heater will likely shorten it’s working life.

There are ways to control when the block heater is working other than going out to the barn to plug it in. Timers and thermostats can be utilized to control the engine block heater to be used only when needed.

Timer Controlled

Using a timer to control the block heater will allow you to have the heater warm the engine for X number of hours prior to when you need to use it. For example, if you want to start the tractor at 6 AM than setting the timer to come on at midnight might be just the amount of time needed to warm up that engine.

Timers should have a rating higher than the wattage of the heater you are using. If a timer has an amperage rating instead of a wattage rating, here’s how to convert watts into amps:

  • Watts divided by volts = amps
  • 400 watts divided by 120 volts = 3.3 amps

Thermostat Controlled

Thermostatically controlled block heaters are most commonly going to be coolant immersed heaters. These types of heaters are designed to plugged in for long periods of time and in order to keep the coolant from overheating a thermostat will shut the heater down when the coolant reaches a certain temp. When the temperature of the coolant falls below a certain degree the heater will turn back on. This keeps the engine coolant within a certain range at all times.

What’s the Best Block Heater for My Tractor?

Some tractor brands sell their own OEM block heaters and then there are several brands of aftermarket block heaters with Zerostart and Hotstart being two of the most popular highly rated manufacturers. Kat’s is another popular brand that has good ratings and a competitive price.

Universal Block Heaters

When it comes to a universal magnetic or freeze plug type block heater, Kat’s will most likely have what you’re looking for. The Kat’s 1160 300 watt magnetic heater is a handy universal engine block heater to have around for multiple tractors or other vehicles. Check out the Kat’s 1160 on

Kubota Block Heaters

BMI makes a 400 watt engine block heater for most Kubota M, B & L series tractors. These thread into a 3/4″ or 1″ NPT port on 3, 4, or 5 cylinder engines. This unit is made in the USA and is the same manufacturer that provides OEM heaters to Kubota dealers. You can also find this heater on

Ford Block Heaters

This OEM replacement freeze plug block heater fits many Ford tractor series starting from the 1970s and up.

It features a removable cord to easily disconnect it in when not in use. This 750 watt heater can be found on

John Deere Block Heaters

While The Green Parts Store and your local dealer will have the engine block heater for your John Deere tractor, there is also JD OEM heaters for sale on if you prefer to shop that way. This one pictured is 400 watts and fits many different John Deere models. Read the description on for the list of models.

Testing and Troubleshooting Block Heaters

If you suspect your engine block heater is not working there are a few ways you can test the heater and troubleshoot a solution or determine the heater needs to be replaced.

  1. Look for any visible signs of damage to the heater or the cord. Check for corrosion on the connections, broken insulation on the wires or loose connections. check for blackened or burned spots on the cord or as much of the heating unit that you can see.
  2. Check to be sure your source of power hasn’t been tripped and any extension cords that are used are in proper working order. If the circuit is tripped it could be caused by two different situations. A short circuit will cause the breaker to trip instantly and an overload condition will sometimes take a little longer for the breaker to trip. The overload could be caused by bad connections or even by an unrelated piece of equipment on the same circuit.
  3. A short circuit condition with the heater can be checked with an ohmmeter by disconnecting the cord and taking an ohm reading between the hot and neutral terminals. A reading of less than an ohm means there is a dead short and the unit is most likely junk.
  4. A reading of several ohms or more could mean the heating element is working correctly. Calculate the exact reading your unit should read by first finding the current in amps: Amps=watts divided by voltage. Then find the resistance by dividing the voltage by the current: Resistance=volts divided by amps. For example: A 400 watt 120 volt heater would draw 3.33 amps. The resistance of the element should be around 36 ohms.
  5. A reading of infinite or many meg-ohms means the heater has an open circuit which could be caused by a broken connection or possibly a burned open element. Broken connections could be fixed and retested but burned elements means it time for a new heater.

The following table shows the typical ohm reading you should expect to get on many common size electric heating elements and what the current draw in amps would be (assuming 120 volt supply).

Wattage Rating of Heating ElementNormal Ohm Reading Amp Draw at 120 Volts
200 W72 Ohms1.66 Amps
300 W48 Ohms2.5 Amps
400 W36 Ohms3.33 Amps
600 W24 Ohms5 Amps
750 W19.2 Ohms6.25 Amps
1000 W14.4 Ohms8.33 Amps
1500 W9.6 Ohms12.5 Amps

Other Considerations

Other factors besides the temperature of the engine block also affect how easily the tractor will start and operate. These include the condition and temperature of the battery, the temperature of the hydro-static transmission, and condition of the fuel.

Battery Condition

A weak or old battery usually gives out on the first cold day of the season. A discharged battery is also in danger of freezing the electrolyte during cold spells causing irreversible damage. A battery that is kept in good condition by keeping terminals free from corrosion will last much longer.

In cold weather it may be a good idea to keep a trickle charger on your battery and making sure there are no loads turned on to draw the charge down. Another consideration is to use an electric battery warmer. Zerostart makes one that wraps around the battery to keep it in tip-top shape for those cold winter starts. You can see it here on

Warming up the Hydro-static Transmission

If your tractor has a HST than having the engine warmed and ready to run doesn’t necessarily mean the whole tractor is ready to go. A cold HST is going to have to get warmed up too before it is working at it’s best. Using a magnetic or stick-on type heater on the bottom of the transmission will help with that.

This Zerostart silicone pad heater has a 250 watt element that is thermostatically controlled to keep the temperature between 270 and 300 degrees. This is a great heater for oil pans, transmissions, and hydraulic fluid reservoirs. Check it out here on

Fuel Gelling

Diesel fuel has a tendency to crystallize or “gel” at extremely cold temperatures. This can be prevented by buying your diesel fuel in the winter because it is already conditioned for the cold temps or you can add an anti-gel conditioner such as Sno-Cat to the fuel already in your tank. Sno-Cat Diesel Fuel Conditioner can be found on

Corey Sitkowski

I love working around our homestead doing chores, building projects, taking care of our critters and livestock, making maple syrup, and messing around with old mechanical equipment.

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