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I've got an excess (4 quarts) of Red Line Synthetic Heavy Shockproof Gear Oil in stock from either my Moto Guzzi or Alfa Romeo project (I don't remember which). The manufacturer says the following:

  • Film thickness greater than an SAE 75W250, yet low fluid friction like 75W90
  • For heavily-loaded racing differentials and transmissions, problem gearboxes
  • Most popular ShockProof product, many racing and specialty applications
  • Many performance racing applications like Sprint, Midget, Dirt Late Model and Quick Change Differentials, Detroit Lockers and spools, NHRA Top Fuel and Funny Car rear ends
  • Not recommended for most synchro applications due to the product's extreme slipperiness
These products contain the extreme pressure additives necessary for ultimate protection road cars and racing vehicles, as well as friction modifiers (except NS) for proper limited-slip operation
  • Fully-synthetic formulas created from polyol ester base stocks, offer excellent lubrication under extreme conditions
  • Ester base stocks and friction modifiers (except NS) provide additional slipperiness to lower operating temperatures by reducing the sliding friction in hypoid gears
  • High viscosity-index (VI) to provide relatively constant viscosity and film thickness with varying temperature change
  • Superior shear stability and reduced oxidation compared to other synthetics and conventional gear oils
  • Exceed API GL-5 specifications
  • Engineered to provide the highest degree of protection and improvement of differential efficiency for better mileage, longer drain intervals, and less wear
The above mentions "extreme pressure additives" and "hypoid gears" which I understand is what we're looking for in a final drive oil.

I've also some Bel Ray Gearsaver Hypoid Gear Oil 80W-90 but any objections to using the Red Line in the FD unit?
 

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Any oil question will draw multiple responses... a point of interest tho':
Penrite one of our oil manufacturers/blenders here in OZ recommends their "synthetic" for CX500 Engine, but their mineral for the final drive, I contacted their technical dept and they felt the Mineral was closer to original spec despite the gear synthetic looking good on the specs sheet- and (the Mineral) more likely to keep the older units "oil tight"...response to mineral vs synth for final drive pasted below.

I am sure their will be multiple people here that use synthetic in the F/Drive and will disagree-just putting it out there...



Hi John
Different schools of thought to this question.
Some want to maintain modern version of traditional style oils (mineral), others want “the best” modern synthetic oils. When the first synthetic oils became available for these applications there were stories of seal swelling and consequent leaking. No such issues now with modern seals etc.

So if your bikes have had seals replaced in the last 20-30 years, chances are you won’t have those types of issues with synthetic oils. In our recommendations we try to match the manufactures specs so you will usually see mineral oils being recommended for bikes of this era.

So the choice is yours but it does come with a small risk if you use synthetics – depending on how well you know the history of your bikes.

Cheers

Penrite Tech Support
 

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That doesn't sound right to me. If the seals swell they would be less likely to leak....

A few people have used synthetic hypoid gear oil in their final drives and I don't recall anyone mentioning them leaking.

I'd be most concerned about the viscosity. Honda specifies Hypoid gear oil in most manuals and API GL-5 in the book for the CX650E (I suspect they are the same thing), SAE 90 above 5c(41f) and SAE 80 below that; Single grade gear oils are not common these days so most of us use 80W90 hypoid gear oil.

And re "mineral" vs "synthetic", both are produced from the same stock but they are refined differently so synthetic has a higher purity and can last longer in some applications (I'd still change the final drive oil every year or 2 anyway).
 

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Hi S/Bob, we might have a slight gentlemans disagreement on this one.;)

When a polymer (rubber/plastic) is not compatible with a chemical the sequence is often....swell->distort->fail (an example of this is when we put gas in an old plastic oil or juice container)

The bottom line from the tech people was:
"it does come with a small risk if you use synthetics "

As most of us are aware the seals in the Final drive need specialised skill/tools to tackle-is it worth the risk?...probably not.
A possible compromise could be a mineral with largely paraffin base -these resist oxidation and moisture well-but thats only conjecture on my part-no data for that specifically in bike drives-but these include Motorex Hypoid and are widely available.
 

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if it just got bigger and didn't fail that wouldn't be a issue-hence the petrol in a plastic bottle example I gave....
many of those "stop oil leak" preparations that you can buy at the auto store only give you a temporary fix because of this factor...
 

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Very true. But as I said, a number of people have reported success using synthetic hypoid gear oil in the FD so I suspect your oil manufacturer's reply may have been an exercise in butt covering.

The main thing is to use something compatible with hypoid cut gears. I can see seal compatibility as something important too but the viscosity is also important. When I got the Dnepr I had many decades ago the PO told me he had been told to use 10W30 in everything. It used so much oil that I started buying it by the case and always taking several bottles if I was going more than an hour from home. Then I met someone who drove a Lada and he gave me a copy of the page in his Chilton shop manual that explained what the various Soviet oil numbers translated to so I started using what it was supposed to have (straight 30 weight in the engine, gear oil in FD, can't remember what the transmission needed) and immediately the trans and FD stopped using any and the engine's consumption dropped to something far more normal.
 

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Re synthetics-The oil manufacturer said a "small risk" of leakage....rather than "Dont do it"...I don't doubt that some owners have used synthetics successfully-possibly effects will also vary from synthetic to synthetic.
Its just that most owners swap the drive units over when they leak given the special tools needed for a rebuild

But agree fully that viscosity, and rating (e.g. for Hypoids) is important.

Enjoyed the gentleman's discussion-cheers.
 

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Something else to note is that not all synthetics are the same. On a different forum a trusted and respected mechanic mentions trying a different synthetic oil if leaks start appearing after changing to synthetic or simply go back to dino oil.
 

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I always chuckle when someone calls conventional oil "dino oil". Petroleum is the remains of plants, not animals and as I said before, synthetic oil is made from the same petroleum stock as conventional oil, it is just refined differently.
 

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I always chuckle when someone calls conventional oil "dino oil". Petroleum is the remains of plants, not animals and as I said before, synthetic oil is made from the same petroleum stock as conventional oil, it is just refined differently.
I don’t understand your point about it being made from the same petroleum stock as it is still different in the end product. To me that is an irrelevant point and still doesn’t change the fact that some synthetic oils do cause some seals to leak. In many cases the oil leaks have been reversed by going back to “dino” oil.
 

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I am not disputing that some things leak when filled with some synthetic oils that don't leak when changed back to conventional oil.

What I'm laughing at is that if conventional oil is "dino oil" (= made from dinosaurs), synthetic would be too. But since they are both made from the remains of prehistoric trees neither synthetic or conventional is "dino".
 

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I am not disputing that some things leak when filled with some synthetic oils that don't leak when changed back to conventional oil.

What I'm laughing at is that if conventional oil is "dino oil" (= made from dinosaurs), synthetic would be too. But since they are both made from the remains of prehistoric trees neither synthetic or conventional is "dino".
Sometimes you have to accept “slang” for what it is I guess. I certainly didn’t coin the term nor have ever wanted to waste the energy to try and change it. I wish you luck with this mission.
 

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Is this the correct oil for thé finale drive. I now it has to be hypoid but this is not mentioned on the label
203336

Thanks
 

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Is this the correct oil for thé finale drive. I now it has to be hypoid but this is not mentioned on the label
View attachment 203336
Thanks
Is it GL5 rated?
Sometimes if you do to the company website there is a specification sheet that has more information than the bottle-I have used such specification sheets to choose coolants and greases

This is what I found on the Australian site for their HD gear oils but cant see an exact match for your product

HP Gear Oil 80W-90 is recommended for use in automotive manual transmissions, hypoid differentials and spiral bevel rear axles/transaxles where an API GL-5 gear oil is specified. Available in SAE 85W-140 viscosity grade.
 
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