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Royal Purple Max Gear 75w90 Gear Oil

Item 45003
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      Review & Installation Video

      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


      • Fully Synthetic
      • Friction Modifier Included
      • Protects Against Wear
      • Reduces Gear Whine
      • 75w90 Weight
      • 8.8" Ford Rear Ends Require 3 Quarts
      • For 1979 to 2017 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 2017 Mustangs and is compatible with other oils. Three (3) quarts of gear oil are required to fill a 8.8" Ford rear end.

      Fitment: 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 Details

      MPN# 01300

      CA Residents: WARNING: Cancer and Reproductive Harm -


      Customer Reviews (78)

      Write a Review

      Ratings Summary

      4.9 out of 5 overall rating from 78 customers

      Installation Time: Less than 1 Hour

      Installation Cost: 0-$100

      • February 19, 2020

        5 2013 GT - DanM Installation Time: Less than 1 Hour

        Seems fine?

        No problems. I am not a chemical engineer but everything works as it should.

        Helpful (0)
      • February 03, 2020

        5 2000 GT - Tony

        Royal Purple

        Royal Purple is the best product for your car needs.

        Helpful (0)
      • December 29, 2019

        5 2003 GT - Bitty

        Quality product

        The royal purple gear lube is yet another find product that you come to expect from the royal purple manufactures

        Helpful (1)
      • August 12, 2019

        5 2003 GT - Santo Installation Time: Less than 1 Hour

        Gear oil

        Worked great whent to ace to get plastic tuneing to help put it in the diff. Works great.

        Helpful (0)
      • August 11, 2019

        5 1986 Other - BanzaiBullitt Installation Time: Less than 1 Hour

        Better than conventional oil

        Royal Purple Max Gear Oil reduces drivetrain power loss to the rear wheels by reducing friction and heat compared to conventional oils. You can feel the difference!

        Helpful (1)
      • July 24, 2019

        5 1989 GT - BlackVertohio Installation Time: Less than 1 Hour

        Royal purple gear lube

        Great lubricant. My choice for any car or truck. I've used it in several mustangs now.

        Helpful (0)
      • July 22, 2019

        5 1990 GT - mustang90

        Royal purple max gear oil

        The best oil on the market.worked great in my mustang rear end

        Helpful (0)
      • July 09, 2019

        5 2007 GT - ChristopherS Installation Time: Less than 1 Hour

        Great product

        Its gear oil I dont think there is much else to say.

        Helpful (0)
      • July 07, 2019

        4 1995 GT - 2BAD4U Installation Time: Less than 1 Hour

        Max Gear

        Put this in my transmission, helped it out. Will likely use again.

        Helpful (2)
      • June 12, 2019

        5 1993 GT - Gj6808 Installation Time: Less than 1 Hour

        Royal purple

        Excellent product. Used in my transmission for easier shifting and in rear end for protection and quiet.

        Helpful (0)

      Questions & Answers (10 answers)

      5 Top Rated Questions

      going to change my diff to a lsd with 4.10 gears, i have an 08 v6 wondering what the difference between the 75w90 75w140 gear oil which would be recommended

      • The differences in the Royal Purple Max Gear Gear Oil, 75w90 and 75w140 would be the viscosity of the oil throughout a temperature range. For moderate driving applications, 75w90 would be best, however, if the vehicle is driven in more extreme driving conditions, the 75w140 would be best for that application. If you are using the vehicle for a particular application, please give us a call and we would be happy to recommend a weight which would be best suitable for your application.

      Helpful (3)

      One of your staff's comments says to use the friction modifier with Royal Purple. But Royal Purple says the friction modifier is in it already and is not needed. So what is the correct answer ?

      • Even though the Royal Purple gear oil does include some friction modifier, we still recommend using the ford friction modifier for better performance but you can definitely just use the Royal Purple gear oil alone. 

      Helpful (1)

      For 6th gen with Torsen 3.73 the owners manual list 1.5 liters and like 3 oz of friction modifier as capacity. Why are 3 quarts needed?

      • Hello! From my understanding it does vary slightly, but its about 2 quarts of gear oil and a bottle of friction modifier which is about 4 oz and you should be good.

      Helpful (1)

      Which is the recommended oil for daily driving and no track or drag use, 75w90 or 85w140? What weight is the factory fill?

      • It depends on the year and model Mustang you have, you should have your answer in your owners manual or by contacting and speaking with your dealership directly.

      Helpful (0)

      I ordered and received my order of 1 qt., not realizing it was only a qt. bottle. When I checked the quantity needed I saw it required 4.25 pints, but the manual also say 75W-140. Your site said this was the correct lube for the car when I ordered it. What do you recommend? 2008 Mustang GT/CS

      Post Your Question
      5 More Questions
      Will this bottle of solution make shifting a manual tremec (2010) 5 speed shift smoother? Does it affect the shifting in a good way? 1 answer
      I'm confused, so to clarify when changing Gear oil do I need 2 or 3 quarts? 1 answer
      On the bottle and in the part description it states - Friction modifiers included, no additional additives are necessary. Is the Ford modifier really required? 1 answer
      How good will this work for the MT82 transmissions. 1 answer
      7.5? 3 quarts are needed for the 8.8 but what about us v6ers. i'd get three to be safe but if i could save an extra 17 bucks that would be nice too. what do you think? 2 answers

      Installation & What's in the Box

      Installation Info

      What's in the Box

      • (1) one quart bottle

      Tech Specs

      Will It Fit My Mustang

      • Boss 302 - 12, 13
      • Bullitt - 01, 08, 09, 19, 20
      • Cobra - 93, 94, 95, 96, 97, 98, 99, 01, 03, 04
      • Cobra R - 93, 95, 00
      • EcoBoost - 15, 16, 17, 18, 19, 20
      • GT - 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 00, 01, 02, 03, 04, 05, 06, 07, 08, 09, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20
      • GT350 - 15, 16, 17, 18, 19, 20
      • GT350R - 15, 16, 17, 18, 19, 20
      • GT500 - 07, 08, 09, 10, 11, 12, 13, 14, 20
      • LX - 87, 88, 89, 90, 91, 92, 93
      • Mach 1 - 03, 04
      • Other - 79, 80, 81, 82, 83, 84, 85, 86
      • V6 - 94, 95, 96, 97, 98, 99, 00, 01, 02, 03, 04, 05, 06, 07, 08, 09, 10, 11, 12, 13, 14, 15, 16, 17