Hey;
lou here gain. Do any of you know anything about 75/140 Royal Purple Synthetic Gear lube and if it is a good product to use in my sportster. I used to hear a lot about Royal Purple products in the past but dont remember muh about them. Thanks in advance for the info.

 

Royal is a good product so are redline and spectro

 

I use it in an '08 UC - so far, clean, noise-free shifting/running, and N is easier to find. I also like being able to see it on the dip stick as it's really purple.

 

75w140 is too thick IMO and your clutch may drag. I would use a 20w50 MC rated oil (Mobil1, Syn3, Amsoil, RP)or maybe 75w90 gear lube. TAke a look at this viscosity chart and you will see 20w50 & 75w90 are pretty close in operating viscosoty. 75w140 is too heavy because your bike has a shared sump with the trans & primary. 75w140 would be great in a TC engine set up where the trans has its own seperate sump.










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I have drained out the heavier weight oil and put in the correct weight.
Thanks

 

A 75w140 gear oil is only slightly more viscous than a 20w50 engine oil, and the two types of oils have different SAE ratings. The numbers are different mostly to differentiate between engine and hypoid gear oil, and do not reflect actual viscosity. If gear oil was labeled 20w50 how many people would accidentally install it in their engines?

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I tried it in my 05 Sporty....was enough to make the clutch drag more noticably than 75w90. Then the 75w90 still didn't feel right so I went to Syn3 which was fine. In fact I'm not a big fan of gear oil in a shared sump anyway because of the sulfur & moly content of gear oils that can sometimes cause clutch slippage. But lots of people run the 75w90 and have no issues. But where I live the bike has many cold starts and motor oil just seems to drag a lot less when cold. Both Syn3 & Vtwin have no moly additives as well. JMHO.

 

" If gear oil was labeled 20w50 how many people would accidentally install it in their engines? "


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Hopefully only the ones that shouldn't own any wrenches. Hard to imagine any one with
common sensewould use " gear oil " in the crankcase unless they were the types who
ask Auto Zone to replace thier windshield wipers for them.

 

I really think more would make the error than we would like to believe, which is why they have the different designations. Some would see only the "20w50" and just buy and install it.

 

I put the ROYAL in my transmission the other day, and went for a ride today. It was about 50 today... shifted quieter seemed to be a little smother...2 cents worth...08 EGC .... with about 5 to 6 000 miles on her...