synthetic Mobil 1 75w90 gear oil

Anyone using this? will it eat seals on an r75/6?
Thanks!

If it leaks go back to dyno, but I have not found problems with Synth on my gearboxes and certain UK based gearbox rebuilders, reckon that using synth in a gearbox will increase the number of miles between rebuilds.

That's what I read on snow bum's site. I was just seeing if anyone has used this specific oil without issues. If the synthetic eats up a seal/gasket, I imagine the dyno will still leak out of the same spot.

I use synthetic on the gearboxes of 2 bikes without issue, from what I can remember people who had seal leaks using synth on engines, had the leaks go away when they went back to Dyno.

I've used semi synthetic without problems and will probably try full synthetic when my current stocks run out. If it doesn't cause leaks I think it's a smart choice both in terms of reducing wear and reducing drag from cold oil.

I use SAE 75W140 (LS) for both, gear box and final drive of my GS. Much better shifting and less heat evolution in the final drive compared to SAE90. No problems with leakages. Additionally, it's much easier to push move the bike in the garage at winter temperatures.

Had my GSPD tranny rebuilt last year by Bruno in CAnada and he returned it with a note…"75W-140 synthetic, it will last you a long time".

Have been ever since.

All good, no leaks.

Aesome, that's exactly what I wanted to hear!

I've seen a number of gearboxes leak oil after using BMWs own synthetic. This was back when Valvoline was making it for them. Every oil blender uses their own formula, so YMMV.

Been using Motul Gear 300 in boxes, shaft housing and bevel drive for some years now. Noticeable difference in gear shifting. Haven't had much leaking but this stuff will find paths that dino doesn't. Must have things well zipped up.

I guess I will just have to post what happens! so many people on both sides of the fence.

I noticed that too even on semi synthetic. Sold me on never going back to dino oil - not as if I have power to waste on oil drag.

What's the power loss considered to be between flywheel and rear wheel 20% ? It's nice to get even a little of that back if a simple change of oil can do it.

Dino oil has an additive in it to soften and swell oil seals, but proper ester synth doesn't.

Mainly because that additive is ester synth.

The problem, if it exists at all, probably comes from the fact that in the US and a few of their colonies, like Oz, tarted up dino can be sold as synth.

I use ester synth in everything but the lawnmower, including transmissions, and synth suspension and brake fluid, the only problem ever was that it was too good a lube for the starter spragg clutch on my VFR - a problem no one else ever seems to mention.

well guys, no leaking yet. The bike now shifts like a dream. Less tractor like, more like a new bike. If this doesn't leak, I'm never switching back!

I will post a follow up in a couple weeks.

You won't be back. THat synthetics gold.

Just wondering if it would be advisable to use synthetic oil in the older Beemer, like the /2s. I've been using synthetics in my other bikes & works well, so I'm curious.

Not for the engine! Old boxers run best with 20W50. What's the handbook advise for the /2 gear box and final drive? If it is SAE90, than you may try out synthetic 75Wxyz. If it doesn't leak, it should be ok.

Thanks Frank! I'm using Red Line heavy shockproof gear oil (75W-250W) in the transmission & FD of my Ural & have several bottles of it. Would this be OK to use or is it too thick? Made the Ural shift smoother, if there is such thing on an Ural, & the FD doesnt puke the oil out of the vent.

http://www.redlineoil.com/Products.aspx?pcid=4
"Film thickness greater than an SAE 75W250, yet low fluid friction like 75W90"

Never before heard of this, acc. to the description it should be OK. SAE90 is really thick at low temperatures.

plus 1 redline for trans and final .... Awesome sauce