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Royal Purple Max Gear 75w90 Gear Oil

Item 45003
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      Video Review & Installation

      Royal Purple Max 75W-90 Gear Oil is a good choice for any Mustang owner who's picking up a new set of rear gears and wants to make sure that they're picking up a reputable, reliable lubrication. One quart of this Royal Purple Grade runs at just about the $16 mark and applying the new gear oil gets one of the three wrenches on our difficulty meter depending on your method of installation, which I'll explain in just a little bit. Now, there are some factors that come into play when picking out your new gear oil, but in order for you to first choose your oil, you'll need to understand their grades because it is crucial in making sure that the gears mesh properly and turn smoothly. Now, this one here is graded at, again, 75W-90. The grading system is measuring the viscosity of the oil, which is a measurement of the thickness of a liquid. Now, the larger the number, the more viscous or thick the oil is. You'd want thicker oil if your car is under heavy weight or load, if you've got a heavier foot and really beat on it, or if you've got big, slow, rougher gears. You'd want a thinner oil if you're running small, fast, and light gears.When you upgrade gears to something like that, or if you're just doing some routine maintenance, the 75W-90 comes in handy. It may vary depending on your new gear's manufacturer recommendations and what would be best for your application so, make sure you're doing a little research into what oil works best for you. Now, this one here from Royal Purple is a multigrade since you're seeing two numbers there, the 75W being the first and the 90 being the second grade. The W after the 75 refers to its winter viscosity grading or rating, meaning it's certified and tested at 32 degrees Fahrenheit. The 90 without the W refers to its heat rating with a certified testing at 212 degrees. A multigrade oil like this doesn't need to be changed out for the different climates it may be exposed to.If you're looking for a grade like this one here, it comes in right around 16 bucks a quart. You want to be sure to learn how many quarts your Mustang needs as it can vary depending on the generation and package. Anytime you're changing gears, you'll need new gear oil, so the installation is pretty involved. Applying the gear oil itself isn't hard, but it really depends on your method. If you're not actually changing your rear gears, but just need to change the oil, you can pick up a gear oil pump and tubing in some cases and it'll get one out of three wrenches on our difficult meter. However, if you're completely changing your rear gears, the process is on the opposite side of the spectrum, getting three out of three wrenches on our difficulty meter because you're completely disassembling the differential when applying that new oil. With that said, the installation can vary from one hour to several. That's going to wrap it up here, so if you're in need of new gear oil and you're leaning on the side of a 75W-90 Royal Purple Max gear oil, you can grab them right here at

      Product Information

      Features, Description, Reviews, Q&A, Specs & Installation

      Features & Specs

      • Fully Synthetic
      • Friction Modifier Included
      • Protects Against Wear
      • Reduces Gear Whine
      • 75w90 Weight
      • 8.8" Ford Rear Ends Require 3 Quarts
      • For 1979 to 2023 Mustangs


      Pure Performance. Maximize performance from your Mustang's drivetrain with Royal Purple Max Gear oil. This fully synthetic oil is the perfect complement to new gears, lubricating better and ensuring your differential keeps working its best whether it has gone a thousand miles or a hundred thousand.

      Protect Your Investment. Made with Royal Purple's innovative Synslide® additive, Max Gear oil is perfect for upgrades or routine service. It's the gear oil of choice for greater wear protection and lower temperatures for every car, from daily drivers to track-day toys. It prevents corrosion and meets all warranty requirements, so adding Royal Purple Max Gear oil is great for peace of mind when it comes to your Pony.

      Includes Friction Modifier. Unlike other oils, all viscosities of Max-Gear® are formulated with hypoid friction modifiers necessary for use in clutch or cone type differentials. No additional additives are necessary.

      Application. Royal Purple Max Gear 75w90 weight oil is recommended for use in 1979 to 2023 Mustangs and is compatible with other oils. Three (3) quarts of gear oil are required to fill a 8.8" Ford rear end.

      Royal Purple 01300

      CA Residents: WARNING: Cancer and Reproductive Harm -

      Installation & What's in the Box

      Installation Info

      What's in the Box

      • (1) one quart bottle


      Customer Reviews (90)

        Questions & Answers

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