Will Mixing Greases Kill Your Tractor?

In today's video, Tractor Mike answers a viewer's question about switching grease types on a used John Deere tractor. The tractor has always been greased with polyurea grease, and now the viewer is considering switching to synthetic grease. Is it safe to mix greases? What happens if they’re not compatible? Should you be concerned about grease compatibility? We reached out to Wes from AET Systems, Inc. (parent company of Lube Shuttle) to help explain grease compatibility, types of greases, and what to do when switching to a new grease. What Makes Up Grease? Grease is made up of three main components: Base Oil – The primary component, making up 80-90% of the grease, provides lubrication to reduce friction in your tractor’s moving parts. Thickener – Acts like a sponge, holding the base oil together and giving the grease its consistency. It helps the grease stay in place and offers long-lasting protection. Additives – These improve the performance of the grease, preventing rust, resisting water washout, and offering protection under extreme pressure. Understanding grease compatibility is crucial. Mixing incompatible greases can cause "grease bleed," where the oil separates from the thickener, leading to insufficient lubrication and premature wear. Polyurea Grease Compatibility Polyurea grease is commonly used in John Deere tractors due to its stability and long life. There are two main types: Shear-Stabilized Polyurea Grease: These are compatible with most other greases and can be mixed without major issues. Non-Shear-Stabilized Polyurea Grease: These should not be mixed with other greases, as they can cause grease bleed and breakdown. If your tractor has been using polyurea grease and you’re switching to synthetic grease, identifying the type of polyurea grease already in use is essential. Shear-stabilized greases offer more flexibility in switching, while non-shear-stabilized greases pose a higher risk of incompatibility. What Happens if Greases Aren’t Compatible? Incompatible greases can result in grease bleed, where the oil separates from the thickener. This means the oil will run out of the bearing or joint it’s meant to protect, leading to rapid wear. Since it’s impossible to know exactly what grease is already in your used tractor, you won’t be able to flush all the old grease out. So, what’s the best approach? Best Advice for Switching Greases The simplest advice is to try the new grease and monitor its performance. If the oil bleeds out quickly, this is a sign the greases aren’t compatible. In that case, increase your greasing intervals until the old grease is flushed out. For most small tractors, the pressure on bearings and joints isn’t extreme. These machines typically don’t operate under high-speed conditions or heavy loads, so the type of grease isn’t as critical. Consistency in greasing is more important than the grease itself. Regular greasing ensures your tractor stays well-lubricated and performs optimally. Conclusion For the viewer with the John Deere tractor, the key takeaway is to find a grease you like and start using it. Don’t worry too much about switching from polyurea to synthetic grease, but keep an eye out for excessive grease bleed. If that happens, increase your greasing frequency to help flush the old grease out. In the end, regular greasing is more important than the specific type of grease used. Timestamps: 0:00 – Introduction to Grease Compatibility 2:15 – What Makes Up Grease? Base Oil, Thickener & Additives 4:30 – Polyurea Grease: Shear-Stabilized vs Non-Shear-Stabilized 6:45 – What Happens When Greases Aren’t Compatible? 8:00 – Practical Advice for Switching Greases on a Used Tractor 10:00 – Why Consistency in Greasing Matters More Than Grease Type 11:30 – Conclusion & Key Takeaways LINKS YOU NEED TO KNOW ABOUT... Tractor Mike Website/Fun Store: https://asktractormike.com/products-f... Support the Tractor Mike Channel:   / tractormike   Amazon Affiliate Page: https://www.amazon.com/shop/tractormike Contact us at: [email protected] Copyright 2025 Tractor Mike LLC