Royal Purple01300 Max Gear 75W-90 High Performance Synthetic Automotive Gear Oil , 1 Quart (32 Ounces)

Purchased for the front and rear diff in my Durango SRT. I had a "clunking/jerking" feeling if you would accelerate hard and after reading many reviews, the diff fluid needed to be changed. I was at 50k miles and was supposed to be done at 40 so I figured this would fix it. It sure did. It has the additive in it already and I will say putting this fluid in my Durango made it happy. It was a way better price then the Mopar brand of fluid and works just as well. I did purchase a pump to get the fluid into my rear diff. The front was easy to fill. Royal Purple has always been a great brand and still doesn't disappoint.

Although It(Royal Purple) isn't rated for use in either transmission. I've used Royal Purple's Synthetic gear lube in both of my 6-speed Evolution Big Twins. I've been running Royal Purple in the '88 Road King clone since building it some 35 plus years ago. The synthetic lube has given me good service through the years,. I ride year round and the transmission shifts just as easily cold as it does warmed up. The '92 Softail Springer is both a new addition and a "work in progress. After the six speed modification the bike was slow and somewhat difficult to shift until it got warmed up. After changing out the original gear lube for Royal Purple it shifts easily cold or hot.

I was reluctant to change differential fluid on my Acura 3.5 RL due to its confined location but it turned out to be a great DIY experience thanks to Royal Purple. This oil totally caught me off guard as I was not expecting major improvement over the stock fluid but it really made a world of difference. Performance enhancement is very noticeable. My car more responsive and quieter, the entire power train is slicker thanks to lower friction, now I am kicking myself for not doing this sooner.Tip to DIY: Acura 3.5 RL's differential is in an awkward and confined position but it is actually very easy to change if you acquire the proper tools. First you need a 3/8 "flex head" long handle ratchet, standard ratchet/wrench/breaker bar will reach the drain bolt & filler bolt but you won't be able to turn where as a flex head allows you to "pivot" the handle so it can turn freely. The 3/8 drive tip removes the drain bolt & a 17 mm socket removes the filler bolt. After fluid is drained, attach a 1/2 inch clear hose about 25 inches long to a funnel, then snake the hose from top of engine block down to filler hole to refill. I have seen guys on Acura forums removing passenger front wheel doing this job which is totally unnecessary. Once you acquired proper tools the entire process takes no more than 30 minutes.

This 100% does replace Mazda SG1 gear oil and I'd immediately replace that mediocre junk (that can also be underfilled from the factory) in any Mazda transfer case and rear differential that calls for SG1. Per Mazda, the gear oil has to be GL4 safe, this is.. It needs to be for hypoid gears and contain the right additives, this does. Not many other ones meet this unusual combo and since it does it is legally warranty safe, the very slightly higher viscosity ("weight") rating than SG1 won't void your warranty either, if anything it will provide better protection at the expense of .01 MPG fuel economy. My Mazda 3 AWD turbo immediately took off with far less resistance and far less slowing down while coasting putting this in both gear boxes. *Literally* the best 14 bucks I've ever spent on a car, worth paying a shop to do for you if you have to!

I have a 1991 Mazda Miata. The differential makes noise that usually can't be heard over wind noise, but I can hear it when I am driving beside a concrete wall on the freeway.At least I used to be able to hear it.When I got the car three years ago, I took it into a Miata specialty shop and they determined that it wasn't the gears, but the bearings. They recommended changing the diff with a junkyard diff, which I was not able to do at the time. Instead I have been getting the diff oil changed yearly. That was 40,000 miles ago.For some reason, I heard positive things about the Royal Purple brand. I now have a garage, so I decided to replace it myself this year. When I pulled the diff drain plug, sure enough there was about 1/8 of metal stuck to the magnet in the bolt and I could see the shimmering of the metal in the draining fluid. I filled it with RP, spun the wheels a bit, drained it, and put in a new fill of Royal Purple.Now, when I do the same drive next to the concrete wall, I can still hear the diff, but just barely. I am very impressed. While expensive, since the Miata diff only takes a half liter to fill, it is a minor cost (especially compared to getting regular fluid at a lube place). Maybe this diff has another 40,000 miles left.This has convinced me that there IS A DIFFERENCE when you use a high quality lubricant.