The skinny on thinner gear oil

The skinny on thinner gear oil

Fuels and lubes column

When it comes to lubricants, especially for axles, the stance among fleet owners and operators has traditionally been that thicker viscosity is better. After all, thick lubricants do protect. Gear oil must protect critical hardware within the axle while operating in extremely demanding conditions. Minor damage to an axle can create major headaches from increased downtime and expensive repair.

SAE 80W-90 gear oils use mineral oil as a base, which means more frequent oil changes leading to increased maintenance time. They also thicken substantially at lower temperatures, which can hurt efficiency.

The good news is that thinner synthetic gear oil products are already on the market. Viscosity grades such as SAE 75W-90 and SAE 75W-85 can help fleets gain efficiency benefits without sacrificing the protection that SAE 80W-90 provides. Because of this, lower viscosity synthetic gear oils are growing in popularity.

The benefits of lower viscosity gear oils are being recognized by original equipment manufacturers (OEMs) and oil marketers alike. Most OEMs use synthetic-based gear oil and require its use to maintain warranties. In general, these products tend to have higher tier approvals and feature more claims with respect to cleanliness and hardware protection. Synthetic-based SAE 75W-90 gear oils also prevent oxidation and oil thickening that mineral oils are susceptible to, and thus have longer life versus SAE 80W-90.

SAE 75W-90 maintains a more consistent thickness, or viscosity, across a wide temperature range. It’s thicker when exposed to high heat and thinner under colder, wintry conditions than 80W-90.

The use of 75W-90 gear oil is recognized by OEMs as a contributor to overall fuel economy. When run under real-world line-haul conditions, the use of 75W-90 can improve the efficiency of a Class 8 axle by an average of 0.5% over an axle using 80W-90. Considering that axles themselves are 95% efficient, a gain of 0.5% is significant.

While 80W-90 gear oils can be an attractive option because of low initial cost, when total cost is considered, 75W-90 is a smarter option. It offers efficiency and protection, as well as longer drain intervals, that reduce maintenance costs.

The importance of preventative maintenance

Gear oils for heavy duty axles are not fill-for-life fluids. This means that there is an oil change interval that is determined by the OEM, and it should be adhered to for the best possible axle performance and protection.

Unfortunately, gear oil changes for axles can potentially be overlooked when it comes to preventative maintenance for a variety of reasons. This mistake could mean the difference between the cost of a simple gear oil change and the hundreds or even thousands of dollars it could cost for road breakdown events, loss of on-time performance, repairs and downtime.

In addition to changing gear oil at the recommended OEM intervals, it would be wise to change the gear oil in the axle after purchasing a used vehicle, especially if service records for that vehicle are unavailable. This will help increase the return on
investment and extend the life of your new purchase.

Be sure to use a high-quality gear oil in your vehicle’s axles. An OEM-approved or an SAE J2360 approved gear oil are the best options for your fleet. These gear oils are proven over millions of miles in the field to perform as promised. Visit and click on the Qualified Product Listing (QPL) link to access a list of SAE J2360 approved brands and products.

You May Also Like

Goodyear says tires-as-a-service may help fleets save money

Goodyear said the subscription service can help fleets improve TCO, increase uptime, reduce breakdowns, decrease fuel consumption and more.


Goodyear Tire & Rubber Co. said its new tires-as-a-service (TaaS) offering combines the company’s tires, predictive insights and footprint into one subscription-based solution. Building on the company’s Total Mobility program, Goodyear said that it will manage end-to-end tire service for its customers.

Available for commercial and last-mile delivery fleets in the U.S. and Europe, Goodyear adds its TaaS offering can help save time and improve total cost of ownership through outsourced tire management from this subscription-based solution. According to the company, this is designed to increase uptime, reduce vehicle breakdown events, decrease fuel consumption and more.

Davco Technology appoints Tim West as new president

Before joining Davco, West most recently served as VP of seating and structures, Vehicle Solutions Division at Commercial Vehicle Group, Inc.

PRT launches new strut assemblies for ProMaster, Silverado, and more

These new items cover more than 15 million vehicles and include models such as the 2023 Ram ProMaster 1500, 2023 Chevrolet Silverado, and more.

East opens Aftermarket Parts Facility in Kent, OH

In addition to East trailer parts, the facility will carry common parts for all makes and models, such as airbags, lights, wheel ends and more.

Lucas Oil facilities achieve ISO 9001:2015 recertification

The Quality Management Systems certification included both Lucas Oil production facilities in Corydon, IN.

Other Posts
DuraBrake gets investment from Tiger Lily

Existing Shroff family ownership group will remain meaningful equity owners and continue to make up the DuraBrake senior leadership team.

Phillips, Inland Trailer partner on trailer technology

New builds will have Smart7, Rear-Vu, CargoVision, Permalite Lighting and more. Existing customers will be able to retrofit current trailers.

Akebono expands Severe Duty, ProACT brake coverage for light-, medium-duty vehicles

The nine new part numbers suit a list of vehicles including Chevrolet Express 3500, Ford F350, GMC Savana 3500 and Ram 3500.

New Stoughton HQ expected to be done by Fall 2025

When complete, about 200 employees will work at the new corporate headquarters. Product manufacturing will remain at the current locations.