Royal Purple Gear Oil for diffential. No good??

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MikeStaten

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Changed my rear differential fluid on my 2005 Nissan Xterra with Royal Purple 75w-90 gear oil (correct weight according to manual). Anyway, after reading Amsoil's gear oil test it seems Royal Purple isn't that good. I don't do any serious offroading or heavy towing (just a rowboat on trailer). Should I be concerned that the Royal Purple is no good or will it be fine. So far I've driven about 75 miles and it seems fine. Is Mobil 1 gear oil better than Royal Purple??

Thanks, Mike
 
I for one would not be concerned about RP. However I used M1 75-90 for years with very good results.

I don't think it's a good ides to go by a competors test to determine quality. Ever see a competor praise another companies product?
 
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Amsoil tries to make all other oil look bad. Royal Purple makes a very good gear oil. I would leave it in and not worry about it.
 
The fact that Amsoil might be better doesn't mean Royal Purple is bad.
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I'd leave it in and revisit the issue at your next fluid change.
 
I suspect RP is OK. I don't know if its any *better* than M1, or if its worth the extra money, but there's nothing wrong with it. What would you expect Amsoil to say? "One of our small-market niche competitors is just as good as we are?"
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I notice that Redline and Lucas fared pretty badly too (of course IMO Lucas *IS* garbage, but Redline has a very good reputation for gear oils). I'm not bashing Amsoil- they make great products. I just distrust everybody's advertizing departments equally.
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I have a few overall problems with that test anyway. For one thing, the copper tarnish test doesn't even belong in a test of differential gear lubricants. The standard, proven EP additives for hypoid gears are highly corrosive to copper- so the best-performing hypoid gear lubes are naturally going to fail that test. There's no copper in rear axle gearsets for a reason- so that sulfur-containg EP additives CAN be used. The copper corrosion test is applicable to lubes intended for manual transmissions with brass synchronizers, not to lubes for rear axles.
 
I tried Royal Purple(75w90) in my rears this last time and I do some offroading and towing a 28' trailer loaded for war. I used Mobil 1 last time and although I didnt notice any fuel milelage improvements, I didnt notice anything bad either. A couple of weeks ago I got involved in a deep water crossing, where the entire rear got submerged so I checked it for water contaimination and it was still dark purple after about 13,000 miles and still looked good. Ill see how it looks after 15,000 miles when I change it. Iam going to try Amsoil next and see, but Id say RP is as good as any, better than many.
 
RP is expensive!
From what I gather, I would not use RP in anything.

Right or wrong, it has more bad rap than others.
I have no reason to support them or prove anything. I'll go with a sure thing.
 
Originally Posted By: 440Magnum
What would you expect Amsoil to say? "One of our small-market niche competitors is just as good as we are?"
grin2.gif
I notice that Redline and Lucas fared pretty badly too (of course IMO Lucas *IS* garbage, but Redline has a very good reputation for gear oils). I'm not bashing Amsoil- they make great products. I just distrust everybody's advertizing departments equally.
grin2.gif


+1 Seriously, what did you expect Amsoil to say? Of course they're gonna say their oil is better, they want you to buy it!
 
I didn't expect Amsoil to say there were better oils than theirs but I was concernced that Royal Purple seemed to do worse than Mobil 1 and Mobil 1 is about half the price. The guy at the store talked me into the Royal Purple when I went to the register with the Mobil 1 in hand. I don't mind the extra price, as $20 isn't going to change anyone's lifestyle but I want to make sure that people haven't had any major issues with the Royal Purple.
 
For the past two years I've run RP 75W-140 gear oil in the limited slip final drive of my 1995 3 Series. No complaints.
 
I use Mobil1 75W-90 in the rear diff (C-200) on my 2007 Nissan Frontier. I am very pleased with it. I changed out the FF at around 1500 miles. What a mess. Black, smelly, lots of metallic fur on the magnetic drain plug. Refilled with Mobil 1 and ran it untail about 20,000 and then drained and refilled with same. Mobil 1 stayed clean and claer. Almost no fur on the magnet. I'll let this charge of Mobil 1 in for maybe 50,000 miles. BTW, I don't tow.
 
I haven't heard of any RP caused failures, but it doesn't have many fans here for various reasons, ranging from the high price to Amsoil's test.

Personally, I don't have any complaints with it. I probably have about 9K miles on the RP Max Gear 75W90 in my truck and nothing seems any different from before.
 
I actually think the AMSOIL white paper on gear oil is very well done, but not perfect. If nothing else, it will tell you what the gear oil industry is up to and what they get away with because of very little to no oversight. There is also very little information as to what a GL5 lubricant standard actually is, so the oil industry gets away with whatever they want and you, the customer, is at their mercy.

I don't use AMSOIL gear oils nor do I have any experience with RP gear oils, but I find their test results very useful in picking a gear oil based on what it is good at and not neccessarily what it fails at within your price range. Only you, the customer, know what is required for your rear end lube needs. So pick accordingly.

Where I wish this white paper would have concentrated more for rear diffs is in the SAE110 and 140 grade areas. The only thing I use a 75W-90 for is a front diff and transfer case.
 
You should not be worried at all. Lab tests are one thing, real life is another. I'm not saying the testing is wrong - it's a good paper.

Next time you change out, capture a sample and do a UOA.
 
Originally Posted By: MikeStaten
Changed my rear differential fluid on my 2005 Nissan Xterra with Royal Purple 75w-90 gear oil (correct weight according to manual). Anyway, after reading Amsoil's gear oil test it seems Royal Purple isn't that good. I don't do any serious offroading or heavy towing (just a rowboat on trailer). Should I be concerned that the Royal Purple is no good or will it be fine. So far I've driven about 75 miles and it seems fine. Is Mobil 1 gear oil better than Royal Purple??

Thanks, Mike


I don't want to start an Amsoil bash( seriously not my intent )but as you brought up the White Papers let me just say don't believe they are 100% accurate and that they are the holy bible of gear oils. In my personal opinion those white papers have one use and that is in the out house. Many test results provided that do not match up( not even close )with what mfg's of some of those products provide for data. I don't put any faith in them at all on any brand not just what they said about RP.

I never go to a competitor for info on a product I am interested in. That is a bad idea IMO and I doubt you would ever get an honest and totally unbiased report. I wouldn't ask Amsoil if RP, M1, Lucas, Redline, etc... are any good nor would I ask them about Amsoil. I would ask real world users such as the folks here and on auto forums. THAT is where you can bank on the results( usually - anti RP everything bias on this site for some reason? ).

I have run RP products( and even sold them at one time )since 1990. 2 decades now. Their MaxGear gear oils are some of the best on the market. That doesn't mean there hasn't been a problem with it here or there or that a particular application does not fair better on a different product. That happens with all fluids. As a rule though MaxGear is one of the top 2-3 IMO, and top 5 easy, out there. Use it with complete confidence. If it does not work out try a different brand but I doubt you will have any issues.

I have a 2008 Dodge Ram with a lifetime power train warranty and it has RP MaxGear in it right now front and rear. Wouldn't risk my warranty on a lousy product. Actually, I run it in all my new vehicles/trucks be they MOPAR or GM. Never had a single problem with it.

And to be fair Amsoil makes a great gear oil too if you want another option. Their product line is very good, no excellent, while their marketing not so much(IMHO). In my experience you don't listen to what that companys ays about it's competitors. Others can disagree. Toss the White Papers( or flush them
lol.gif
)and sleep easy with MaxGear in your diff.
 
A lot of people seem to have missed the OP's point. He wasn't comparing Royal Purple to Amsoil, he was comparing it to Mobil 1:
Originally Posted By: MikeStaten
Is Mobil 1 gear oil better than Royal Purple??

Originally Posted By: MikeStaten
I was concernced that Royal Purple seemed to do worse than Mobil 1 and Mobil 1 is about half the price.

Amsoil may be biased one way or another, but at least their whitepaper references standard, repeatable tests. This isn't just some stuff that we have to take Amsoil's word for. Anyone at any of hundreds of labs across the country could go to work today and verify the results. Their choice of tests and the marketing may be questionable, but the results themselves are probably reliable and to some extent useful in and of themselves. This is more than can be said for a lot of the advice you get from people, even on this website.

I'd say the OP's concern was reasonable, even if it was unnecessary.
 
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