fluids for your tractor

Selecting the Right Fluids for Your Tractor and Attachments

Agricultural Equipment, from tractors through to the attachments they use have changed considerably over the last few decades, and fluids for your tractor too.  Driven by performance efficiency and the technology developed to improve it, as our tractors and equipment become more sophisticated, so do their requirements for maintenance and upkeep.

Of all the considerations in this regard, fluids rank right near the top of things to consider.  Let’s examine some of the highlights, and source out some great places to visit to learn more.


Keeping your tractor cool is a major challenge to the engineers who design them.  One of the biggest challenges is that all those heat sources are contained in a relatively small engine compartment…this creates a real challenge to any assistance from the fan(s) that might be used to assist the process.  A large, turbocharged diesel tractor engine, for example, can have up to five cooling systems under one hood.  The engine, the fuel, transmission oil, an air compressor, and the air conditioning in the cab.  Add new emission standards imposed by regulators and you can understand why engineers always keep the headache medicine close by.

Most farm tractors rely almost entirely on one big fan to get rid of all that heat.  Often times, your tractor will indicate it’s ready to overheat, and the reason isn’t because you’re likely low on coolant most of the time.  It’s because your fan isn’t operating properly…most of the time, the screen installed ahead of the radiator and behind the fan is plugged with debris.  Left plugged, your engine will heat to a point where the coolant does in fact break down and boil over, and could potentially cause serious damage to the engine components.  If you find that your tractor overheats regularly due to debris in the screen, chances are, you need to change the fluid and freshen it up; but most importantly, you need to keep that radiator screen clean, and check it more often.

Smaller tractors are actually quite prone to this condition, as their engine compartments are smaller, yet packed with all the components, preventing good air flow away from the compartment.

It is generally recommended to not mix coolants.  Stay with one brand, with the proper cooling and anti-freeze ratings, and change it precisely to the manufacturer’s recommended intervals.

Engine Oil

Believe it or not, oils for tractors are categorized by definition as ‘Engine’ Oil (for use in diesel powered engines); and ‘Motor’ Oil (for use in gasoline powered motors).  Some important considerations when choosing an engine oil include the season and the use patterns, change intervals, type of engine, and other factors.  Always consult the Manual for your make and model for recommended engine oil viscosity; then choose the right oil based on your climate (especially if you have very cold or very hot seasons).  Other rules of thumb include:

  • Always change the filter when changing your oil
  • Never mix oils. Keep records of the type of oil used in your last change, and use only that viscosity (and brand), or change the oil and filter entirely.  If that’s impossible, top off the oil with as close a viscosity as you can, but order the new filter and schedule a change as soon as you can.

There are many tools available from your equipment manufacturer and third party vendors regarding what fluids are recommended for your tractor.  Cenex (or CHS) lubricants offer a lookup tool that allows you to enter the type, model, make, etc. and it will provide you with the specs you need.  See:   Cenex Lubricants Recommendation Tool .  There are others, and the most reliable of course, is your manufacturer, dealer, service rep, etc.

Hydraulic vs Transmission Oils

Older tractors were typically built with separate transmission and hydraulic systems.  Therefore, they had different reservoirs, pumps, and filters.  They require separate fluids for each system.  For example, if you’re looking for oil for the front end loader’s hydraulic system, you most likely need a universal tractor hydraulic fluid, or an ISO-specified hydraulic oil. Refer to the manual, or find it online, or consult with your service technician to determine this.  Once you find the specified weight of oil you need, you may find that some hydraulic oils are labeled “ISO,” and others “AW.” These oils are the same weight, but AW oil also has anti-wear properties, hence the name. AW oils are generally superior to ordinary ISO oils for use in older tractors. Here’s a table to help you convert from ISO to AW:

SAE-to-ISO Oil Conversion Chart

10W 32
15W or 20W 46
20W 68
30W 100

ISO and SAE are standardized specifications that define oil weight. This ensures that one brand’s 30-weight oil is the same viscosity as another’s.

Source:  Which Tractor Hydraulic Fluid Do I Need? – Farm and Fleet Blog

Tractors built after about 1980 are much simpler.  The hydraulics and transmission draw fluid from the same reservoir. With these modern tractors, you use trans-hydraulic fluid. As the name suggests, both your hydraulics and your transmission are using the same fluid.  Always consult your operator’s manual and be sure to use only that specified weight and rating when selecting hydraulic fluid.  Though there are so-called ‘universal’ trans-hydraulic fluids that meet the specifications of most tractor manufacturers, dig deeper to ensure that your make, model, and system is listed; or buy the product that is.

Though filter changes for your transmission/hydraulic fluid may be at a somewhat wider interval than engine oil, they are just as, or more important.  Further, it is important to understand how your hydraulic system vents, so that if you are changing your own hydraulic fluid, you don’t end up with troubles caused by air pockets.  Most small farms look to their dealer or service specialist to change hydraulic fluids.

Gear Oil: perhaps the most commonly overlooked fluid for tractor operators is Gear Oil.  You hook up the rototiller or mower or other implement, you check your engine, hydraulic, and coolant levels, top them off, and then hit the field ready to work.. you kick in the PTO, and your implement does its thing, driven by a shaft coming from a tractor PTO at 2200 RPM’s (that’s a lot of torque!).  When you think about it, the gears or chains or belts driving that implement had better be protected.  That is where Gear Oil could be the most overlooked but most  important part of the fluid ‘things to do list’.

Gear oil is designed to protect some of the most vital components of your equipment.  Gears, bearings, axles, differentials, transmission components, and power take off units (PTO).  Gear oil generally has higher viscosity for better distribution and protection requirements through the specified gear set it is protecting.

When selecting Gear Oils, always use the OEM-specified product or a product guaranteeing equal quality. With a longer change interval than other fluids, it might be tempting to use an off-brand or off-spec product.  Don’t do it!  That doesn’t mean it is a fluid that isn’t as important.  In fact, with a longer change interval, it’s even more important to choose the highest quality product, exactly to manufacturer’s specifications.  Premium gear oils include anti-wear additives to increase durability, as well as dispersants to reduce sludge and carbon varnish buildup.  Further, each implement has different drive speed specifications (which relates to temperature and wear), so choosing the right Gear Oil by the tool it is for is very important.

Inspect your gear oil for signs it has not been maintained (this is important when buying used equipment).  Like engine oils, gear oils will break down and show signs of oxidation, or contain debris.  In time, gear oil will become excessively thick viscosity.  These elements of breakdown allows for friction, gear wear, grinding, and costly repairs (most often when you least want them..in the middle of the field)

Cenex (see above) and other sources, all have lookup tools to assist you at finding the right fluid for the right purpose…and whenever possible, refer to the manual for each component of your ag equipment arsenal..whether in the shop, or online from the manufacturer.  Most importantly, DON’T PUT IT OFF!!

Read more about it:

Choosing Gear Oil Lubricants – CENEX

Which Tractor Hydraulic Fluid Do I Need? – Farm and Fleet Blog

CENEX Lubricants for Agriculture

Cenex Lubricants Recommendation Tool

Tractor Supply – how to choose the right lubricant

Powerpoint Presentation – Univ of California Davis – Understanding Fluid Lubricants in Ag Equipment

Central Valley (CA) Ag Coop – Selecting the Right Oil

Keeping Tractors Cool – American Society of Mechanical Engineers

Article and Video:  CENEX Expert Blog – Hydraulic Fluid for your Tractor


Penn State – Bio Based Fluids – Presentation at the New England Farm Energy Conference

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