Sythetic or not

[Nacho]

I just drained my 582 E-Box and filled it with a full Synthetic gearbox oil. Anyone ever had issues with full Synthetic oil in the gearbox? I beleive in the best qaulity oil for my machine and gearbox. It meets all the Rotax min specs. Any comments. Dont want to start a debate on oil again, just wanting to know if anyone ever had any issues with this

CASTROL SAF-XJ
DESCRIPTION:
Castrol SAF XJ is a fully synthetic SAE 75W-140 hypoid gear oil formulated for use in both conventional and limited slip differentials.

APPLICATION:
• While being suitable for all applications where a lubricant of this quality is specified, it is specially
formulated for use in limited slip differentials fitted to Japanese vehicles requiring an SAE 75W-140
extreme pressure gear oil.
• Castrol SAF XJ has additionally demonstrated outstanding performance in competition vehicles
employing limited slip differentials.

SPECIFICATIONS:
• SAE 75W-140
• API GL-5
• BMW Approved
• ZF TE-ML 05 Approved

Castrol SAF XJ is also specifically designed for BMW differentials including the Z3 limited slip differentials.

[ZULU1]

In my experience with synthetic it is possible that it needs to run hot and hence boil off water ingress, not saying it will happen but synthetic oil is hydroscopic and as its used in BMW M5s etc they have oil temp gauges reading at 140 degrees. Needs to get rid of excess moisture. The HKS needs synthetic so i used to run it as hot as I could for that reason. Cant see a gearbox getting to 100 degrees. Maybe stick with a mineral oil...

Never heard of gearbox fail in a Rattex as yet.

[OzGyro]

Hi All

Nacho - Dont panic and stick with your choice of going to a synthetic oil, you will have few regrets if any, if you can justify the extra expense in comparison to a mineral grade oil then you dont have a problem.

There are numerous types of synthetic oils available on the market today, the most prevelant are PAO (Polyalphaolefin), PAG (Polyglycol) and E (Esther), each has there advantages and disadvantages as such. PAO synthetics are hydrophobic, whilst PAG and E oils can be hydrophillic and can react in the perscence of oil.
I would be extremey interested to see any modern motor vehicle that has an oil reach a constant 140 degrees Celcius, it may happen in high performance race cars but is very unlikely in a passenger vehicle application and if it does then you would only reccomend the use of a synthetic oil, synthetic oils have a much higher tollerance to heat and have a much better oxidation resistance than conventional mineral oils, all these poperties are extremely desirable for extended high temp operations.

Just to give it some perspective, lets say an oil is designed to operate at a continual temperature of say 60 - 70 degrees Celcius, for each 10 degree increase in temperature above that value the rate of oxidaton (a very undesirable property) in that oil approximately doubles, or in other words the serice life of the oil is approximately halved.

I hope some of this makes sense, dont be scared of synthetics and their applicatons, the only thing that can be a bit scary at times is their price.

Regards & Safe Flying
Darren

[skybound®]

Being at the coast, will not use synthetic owing to it's hydroscopic properties. You dont want the stuff that is meant to be protecting you from moisture - being the culprit for keeping the moisture in the first instance.

[OzGyro]

Hi All

Skybound, I am a little perplexed by your logic. If what your saying is true, then I guess every single late model Car, motorcycle, boat etc in Cape Town, Durban and alike are in serious trouble. Im really interested in hearing on what basis that you think all synthetic fluids are hydroscopic.
Hydrophobic synthetics with long chain hydrocarbon compounds actually form a hydrophobic surface on bearing steels, something that I see as a distinct advantage. Demulsibility (the ability to release water) is something else that you may also want to consider. There are typically two types of water in any given system, free and entrained water, free water is far easier to identify and deal with, entrained water on the other hand can be extremely difficult to recognize. Water at levels as low as 200 ppm (0.02%) can have a negative impact on oil useful life, in industry water ingress can shorten roller bearing life by up to 80%.
When it comes to water, there are three key considerations
Keep the water out in the first place.
Remove it before it can do harm.
Change the water into something else.
Its like pretty much everything in life, prevention is better than cure. Treat the cause not the symptoms.

Regards
Darren

[Nacho]

Thanks for the info. I just like to use the best, if I can. The full Synthetic gearbox oil is R80 for 500ml. You use +- half a bottle in your gearbox, and that lasts for 100hrs. I don't think that is too heavy.

I use CASTROL SAF-XJ for my gearbox and my 2 stroke is CASTROL POWER 1 RACING 2T.

The 2T works out +- R900 for 12l. This is pricey, but lasts me about a year, so not that bad.

In my 503 Windlass I use FUCHS SPECIAL TWO STROKE OIL. Which is a mineral oil meeting the Rotax min requirement. This is +- R600 for 20L

PERFORMANCE LEVELS
• API TC
• JASO FC
• ISO-L-EGC

I never had issues with either of the oils used above. The 582, I am using the Full Synthetic Castrol oil, is a old Silvertop. So in my mind I am just giving her some special attention She is also a auto-lube machine, so her two stroke usage is also not as heavy compared to when you pre-mix. (Which concerns me sometimes ) I am a bit weary of the auto-lube systems, but the guys that uses them assures me they never had any issues.

[skybound®]

Hi All

Skybound, I am a little perplexed by your logic. If what your saying is true, then I guess every single late model Car, motorcycle, boat etc in Cape Town, Durban and alike are in serious trouble. Im really interested in hearing on what basis that you think all synthetic fluids are hydroscopic.

I am not in a position to say all are hydroscopic. Did a test when I first bought a trike - it was a test passed on by one of the gurus back then. Take some synthetic oil, place in a frying pan, heat a little, then add a drop or two of water. If the oil disssapeared - it was hydroscopic. Do the same with a mineral based oil and the two liquids remained seperated. This may be simple logic and perhaps even the gurus that passed the test on at that stage may have been misinformed - but to me - moisture is what causes the oxidation - so anything that may contain water is not good.