6 Best Oil Filter Sandwich Plates For Auxiliary Cooling

Keeping your tractor or irrigation pump running through the peak heat of summer demands more than just checking the oil level. Auxiliary oil cooling prevents thermal breakdown in hardworking engines, especially when those machines are tasked with long hours of heavy towing or stationary PTO work. Installing a sandwich plate is the most straightforward way to add that extra layer of thermal protection without major engine modifications.

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Mishimoto M20: Best Overall Thermostatic Plate

The Mishimoto M20 stands out because it integrates a reliable thermostat that dictates exactly when oil starts flowing to the auxiliary cooler. By bypassing the cooler until the oil reaches roughly 185°F (85°C), it ensures the engine reaches operating temperature quickly, even on chilly spring mornings. This is critical for preventing moisture buildup and sludge formation during short, intermittent work cycles.

Construction quality is the primary reason for this plate’s reputation among those who maintain their own equipment. The aluminum housing is robust enough to handle the vibration of older diesel engines without fatigue or cracking. The inclusion of M20 ports makes it compatible with a wide array of agricultural engine blocks.

Choose this unit if the machinery experiences frequent cold starts followed by heavy mid-day labor. It offers the best balance of longevity and engine-health monitoring for equipment that demands a precise operating environment. For most hobby farm applications, this is the gold standard for reliable thermal management.

Derale 15735: Top Choice for Heavy-Duty Use

When the equipment is pushed to its absolute limits—think heavy tilling or constant operation in triple-digit heat—the Derale 15735 is the heavy lifter. Its design focuses on high-volume flow and durability, utilizing a robust bypass system that handles thick, high-viscosity lubricants common in older machinery. It is built to survive the harsh realities of dusty, high-vibration work environments.

The unit is slightly bulkier than its competitors, but that size correlates directly to its structural integrity. The reinforced internal pathways reduce the risk of flow restriction, ensuring consistent pressure even when the oil is heavily taxed. It provides peace of mind for high-hour tractors that simply cannot afford an overheating event.

Select this model if the farm equipment is older, larger, or consistently pulling heavy loads. While it is more expensive and physically larger than a basic plate, the durability provided by the Derale 15735 is unmatched for serious agricultural work. It is an investment in the long-term survival of the engine.

GlowShift M22: The Best Budget-Friendly Option

Not every piece of equipment on the farm requires premium, high-cost cooling components. The GlowShift M22 is the ideal solution for hobby farmers who need functional auxiliary cooling on a restricted budget. It covers the basics effectively, providing the necessary ports for oil lines without excessive bells and whistles.

While it lacks the sophisticated internal thermostat found on more expensive models, it works perfectly for simple, constant-load cooling setups. It is straightforward to install and compatible with common thread sizes, making it a reliable choice for utility vehicles or garden tractors. The machining is consistent, ensuring a good seal even at a lower price point.

Use this plate for machinery that doesn’t see extreme daily use or for a quick, effective cooling upgrade on a secondary tractor. If budget is the primary constraint and the environment isn’t consistently sub-zero, the GlowShift M22 gets the job done without over-complicating the setup. It is honest, effective, and keeps funds available for other essential farm maintenance.

GReddy QX-01: Ideal for Tight Engine Bays

Space is often at a premium under the hood of compact tractors or specialized harvesting equipment. The GReddy QX-01 features a low-profile design that minimizes the distance the oil filter extends from the engine block. This prevents interference with steering linkages, cooling fans, or other chassis components that are often crammed into small engine compartments.

Despite the compact footprint, it does not sacrifice flow capacity. It provides the necessary throughput for efficient cooling while maintaining a slim physical profile. Its build quality is high-grade, ensuring that the critical connections remain leak-free even when mounted in awkward or restricted spaces.

Opt for the GReddy QX-01 when mechanical clearance is the deciding factor in the installation. It is the best choice for modifying smaller machinery where traditional, thicker sandwich plates simply will not fit. Choosing this plate ensures the work gets done without requiring a complete redesign of the surrounding engine components.

Speedmaster Universal: Most Versatile Adapter

The Speedmaster Universal is designed for those who work with a variety of engine types across their property. Because it uses a multi-fit approach, it can be adapted to fit different filter thread pitches, making it an excellent “spare” to have in the workshop. Its versatility makes it a favorite for those managing a mixed fleet of older and newer machines.

The unit is relatively simple and follows a traditional flow-through design. While it may lack specific specialized features like integrated thermostat housings, its universal nature allows for a custom cooling setup that can be tailored to almost any application. It is the go-to for custom rigs and unique, vintage engine configurations.

Consider this option if the farm features a variety of equipment with non-standard engine blocks. It serves as a reliable, adaptable base for building a custom oil cooling system. For those who enjoy the challenge of retrofitting old iron, the Speedmaster provides the necessary platform to keep everything running cool.

Perma-Cool 189: Easiest Plate for DIY Installs

The Perma-Cool 189 is favored for its simplicity and ease of installation. Everything included in the kit is designed to be intuitive, minimizing the time the machine needs to be out of service during the installation. The layout of the ports is logical, making it easy to route lines in a way that avoids sharp bends or potential pinch points.

Beyond the hardware, the plate itself is lightweight and compact, placing less stress on the factory oil filter mounting stud. It serves the basic purpose of providing a clean, accessible location for oil cooler lines. For the hobby farmer who wants a straightforward project without unnecessary complexity, this is the most user-friendly choice.

Choose the Perma-Cool 189 for a quick, efficient project that gets the equipment back in the field with minimal downtime. It is perfect for those who want a reliable, no-nonsense cooling upgrade. Once installed, it is easily serviced, making it a practical choice for long-term farm maintenance.

How to Pick the Right Plate for Your Equipment

Choosing the correct sandwich plate starts with identifying the specific thread pitch of the factory oil filter housing. Mismatched threads lead to catastrophic leaks and potential engine damage, so double-check the manufacturer specifications before ordering. A common error is assuming that a standard thread size fits all, but tractor and automotive engines often vary wildly in their mounting requirements.

Next, consider the available space between the filter and the engine. If the area is tight, a thicker plate might force the filter into the path of an exhaust manifold or a steering rod. Always measure the clearance to ensure that the filter and plate assembly will not rub against any surrounding components during the natural vibrations of the engine.

Finally, evaluate the workload of the machinery itself. A machine that only runs for twenty minutes at a time in mild weather does not require the same cooling capacity as a tractor running a bushhog for six hours in July. Match the plate type—specifically whether it includes a thermostat—to the operating conditions of the machine.

Thermostatic vs. Non-Thermostatic: Which is Best?

Thermostatic plates are the smarter choice for machines that operate in variable climates or perform sporadic tasks. By keeping the oil within an optimal temperature range, the thermostat prevents the oil from staying too cold for too long, which is a major contributor to internal engine wear. In colder regions, a thermostat is essentially mandatory to ensure the engine warms up properly.

Non-thermostatic plates offer a simpler, more robust alternative for machines that are either always under heavy load or operate in strictly hot climates. With fewer moving parts internally, there is technically less to go wrong within the plate itself. However, they can lead to over-cooling in engines that are not being worked hard enough to generate significant heat.

For most hobby farms, the thermostatic plate is the superior investment. It protects the engine across the full spectrum of seasonal changes. Only choose a non-thermostatic plate if the specific application is a high-demand, single-purpose engine that stays at peak operating temperature for the duration of its use.

Key Steps for a Leak-Free Sandwich Plate Install

Preparation is the secret to a leak-free installation. Before bolting on the plate, ensure the surface of the engine block around the filter mount is clean and free of old gasket material or paint. Even a tiny piece of debris or a small burr on the mounting surface will compromise the seal and lead to a persistent, slow oil drip.

Always lubricate the new O-ring seals with a light coat of fresh engine oil before tightening the sandwich plate into position. This helps the seal seat correctly and prevents it from pinching or tearing during the initial assembly. Never over-tighten the adapter nut, as the aluminum housing can crack or deform, rendering the unit useless.

Ensure that the oil lines are routed securely, using vibration-dampening clamps to keep them from rubbing against sharp metal edges. If the hoses are constantly vibrating against a bracket, they will eventually fail, creating a massive mess in the field. Always keep a few extra feet of hose and spare fittings on hand to avoid being stuck mid-project.

Checking for Leaks and Common Troubleshooting Tips

After the installation is complete, run the engine at idle for several minutes while closely watching for signs of weeping at the plate-to-engine interface. Check the fittings on the lines as well, as these are common spots for small leaks to develop once the oil pressure reaches its maximum. If a leak appears, resist the urge to simply tighten the nut further; often, the O-ring needs to be repositioned or a fitting requires a bit of thread sealant.

If the oil temperature fails to rise, the thermostat might be stuck open, or the oil is being cooled too efficiently for the engine’s current load. Conversely, if the temperature gauge spikes rapidly, check for air bubbles trapped in the new oil cooler lines. Bleeding the cooling circuit is sometimes necessary, especially if the cooler is mounted higher than the sandwich plate itself.

Lastly, make it a habit to check the sandwich plate during every routine oil change. Vibrations from field work can loosen fittings over time, even with proper installation. A quick visual inspection and a gentle touch will reveal potential issues long before they turn into a major loss of oil.

Properly implemented, an auxiliary cooling system turns a vulnerable, overworked engine into a reliable farm workhorse. Choosing the right sandwich plate is the first step toward preventing the thermal fatigue that eventually sidelines so many machines. Whether prioritizing budget or heavy-duty durability, the key remains consistent maintenance and a careful, deliberate installation.