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I was thinking how we could up the hp in our FX's when I remembered a clip from Hot Rod TV. They drained the engine oil, trans fluid and differential fluid from a Ford. The fluids were replaced with Royal Purple synthetics. They dynoed it afterward and it gained some ponies. There are numerous articles from various magazines at their website royalpurple.com showing hp and mileage gains from various foreign and domestic cars. Less friction = more hp.

I just changed over to Mobil 1, but am planning to use their diff oil soon. Looks very easy to change the diff oil. The pumpkin has two plugs, one to drain and one to fill, so it's a no brainer. All you need is a 3/8 ratchet to get the plugs out. Going to stay away from changing the trans fluid, too expensive of a item to not be covered by warranty if it were to take a puke. Since our FX's have a IRS there will probably be a smaller gain in hp than if we had a solid rear axle since the wheel bearings are isolated from the diff, but I think it's worth a try.

Stock takes 80W90 oil, Royal Purple only makes a 75W90 that will be compatable.

If you plan on doing this there is no capacity available, but the pumpkin is small so I'm guessing that one quart will be enough. When filling the diff up, fill to just under the fill hole. Just stick your finger or a screwdriver in there to see how much it is full, put the plug back fill plug back in, (of course you put the drain plug in before filling) :wink: and you're done.

I'm a mechanic, not very familiar with foreign makes, but have learned much from reading at this hellacool website.
 

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Capacities:

Front differential = 1 3/8 pints, API GL-5 gear oil
Rear differential = 3 pints, API GL-5 gear oil
Transfer case = 2 5/8 pints, Nissan Matic "D" or Dexron/Mercon
Transmission = 10 7/8 quarts, Nissan Matic "J"

Royal Purple 75-90 gear oil is perfectly fine as it meets GL-5 requirements.

Royal Purple transmission is okay to use in the transfer case, it is a synthetic Dexron/Mercon. DO NOT use it in the automatic transmission, it is not an equivalent to Nissan Matic "J" and will void warranty.

I'm running Mobil 1 5w-30 and Royal Purple 75-90 gear oil, can't really notice the power increase, but milage increased by 0.5 MPG.
 

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Royal purple is expensive stuff.
 

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Are Synthetic Motor oils really more beneficial? (Mobil 1, Royal Purple, etc.) I mean you'll be changing every 3000 / 3750 anyway, why the added expense, unless life of engine, running cooler, and MPG is REALLY improved ?
 

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PINITI-FX said:
Are Synthetic Motor oils really more beneficial? (Mobil 1, Royal Purple, etc.) I mean you'll be changing every 3000 / 3750 anyway, why the added expense, unless life of engine, running cooler, and MPG is REALLY improved ?
No reason to change teh synth at 3K. You can, but not necessary. Closer to 7500 each one, so the twice the price comes out about the same.
 

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Even if you balanced it out and changed at every 5000, what are all the benefits? (btw, nice STB pic.)
 

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GEAUX said:
PINITI-FX said:
Are Synthetic Motor oils really more beneficial? (Mobil 1, Royal Purple, etc.) I mean you'll be changing every 3000 / 3750 anyway, why the added expense, unless life of engine, running cooler, and MPG is REALLY improved ?
No reason to change teh synth at 3K. You can, but not necessary. Closer to 7500 each one, so the twice the price comes out about the same.
really? I use mobil 1 5w-30 and changed it every 3000.... but now i change every 3750...
 

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shong43826 said:
GEAUX said:
PINITI-FX said:
Are Synthetic Motor oils really more beneficial? (Mobil 1, Royal Purple, etc.) I mean you'll be changing every 3000 / 3750 anyway, why the added expense, unless life of engine, running cooler, and MPG is REALLY improved ?
No reason to change teh synth at 3K. You can, but not necessary. Closer to 7500 each one, so the twice the price comes out about the same.
really? I use mobil 1 5w-30 and changed it every 3000.... but now i change every 3750...
That should be fine.

Kinda like a pulley. Nothing really making horsepower, but allows something else not to absorb as much, thus more output.

I imagine the lubricants work in the same manner. For the 2 years, the dealership is changing everything, so it is what they put in, but after that, I may go to synthetics.

Thanks Pin on the STB comment. Do you think the piece removed on the intake will make a difference?
 

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The quality of all of our good oils today is much,much better than just a few years ago and much better than 5-10 years ago.I have used syn(Mobil 1 ) exclusively and you could eat off thoses motors after 100000 miles.Yes you can extend the service cycle,but I do not

Mileage improves,wear is reduced ,power fractional,and it will find a way to leak!
 

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So re: syn. oil is Mobil 1 the best & only way to go, or is Royal Purple a quality alternative?
 

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PINITI-FX said:
So re: syn. oil is Mobil 1 the best & only way to go, or is Royal Purple a quality alternative?
Mobil 1 is one of the better synths and chosen by many manufacturers. That is the one that I ran in my C5s because GM put it there to begin with.

Never ran Royal Purple ,but many do and love it.

Recently, I read/heard that Castrol has been having problems with the correct blend and as a consumer stay away if you are wanting the true effects of synth.
 

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I hear nothing but wonderful things abour Amsoil, but Mobil1 is much more accessible, so that's what I went with.
 

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Synthetic Oil

I personally feel AMSOIL is about the top of the line for synthetics. I've been using it since the early 1970's. They make a complete line of products from 2 cycle oil to gear lube, etc.
 

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Im a fan of royal purple , I had it installed in my car and noticed it ran alot smoother. Great oil..
 
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