Gear Box Oil

[LONG_KEELER]

Does it really matter if you put engine oil in a small outboard's gearbox ?

When I had diesel engines, the oil for the gearbox was often the same as the engine sump.

 

[peter gibbs]

As you may know, gearboxes mostly sustain more torque so need heavier guage oil. I use Comma 75-90 guage G5. Not expensive- the precise spec for your ob or similar hp is on line.

PWG

 

[VicS]

It would be better than no oil but modern outboard gear boxes use an EP gear oil .

An outboard gear oil , which they tell us contains additional emulsifying agents and corrosion inhibitors compared to automotive gear oils is usually recommended.

 

[Topcat47]

It would be better than no oil but modern outboard gear boxes use an EP gear oil .

An outboard gear oil , which they tell us contains additional emulsifying agents and corrosion inhibitors compared to automotive gear oils is usually recommended.

+1 on that. Outboards are generally much higher reving than inboards and the gear oil takes quite a pounding. Depending on your outboard, the gearboxes don't take a lot of oil (I'm talking about sub 8hp here if you've a pair of 60's you might not think the oil capacity is trivial). Gearboxes are more expensive than gear oil.

 

[LONG_KEELER]

Thanks chaps.

Yes. Outboards higher revving than a diesel donk.

Result

Got the Comma Oil from my local car parts store at £4.99 for 1 litre. My previous Quicksilver oil was over £20 for 1 litre. Should do my three small outboards comfortably.

 

[QBhoy]

Yeah. Some older VP outdrive gearboxes were spec’d as “same as engine” and about a 30w. Things have changed a little since. Lots of reasons why to be honest. Things like short term ability to deal with water ingress would be one reason. Dog clutch/straight cut gearing and their requirement for a more robust synthetic oil would be another, compared to an inboard gearbox like you may be used to. Apart from that...there is no reason I can think of at all, not to use what the manufacturer recommends. Especially on a small outboard.

 

[Skylark]

...there is no reason I can think of at all, not to use what the manufacturer recommends.

Good advice.

I worked for a gearbox manufacturer for 10 years.

It’s especially true if the engine maker recommends an oil with specific additives. Quicksilver is a good example. Additives are generally there for good reason.

 

[jdc]

I have used engine oil in the gearbox of an outboard, but that was when I used Castrol Agri 'MP' , aka 'STOU', for my engine oil. The relevance is that STOU oils are designed for transmissions as well as engines, so simultaneously it's CF-4 / 10W30 (for the engine) and GL-4 / EP-80 for the transmission. EP-80 is what the outboard required (Lord knows if GL-4 was the right service category, the OB user manual didn't say).

 

[Adios]

Any thoughts on this Castol gearbox oil? Castrol 18037160 80W-90 1L Castrol Axle EPX Oil: Amazon.co.uk: Car & Motorbike Quicksilver in tubes is around £40 a litre now. Surely there's a good quality alternative?

Blurb reads: "To prolong the life of your vehicles axles and their components it is vital to keep them topped up with a suitable axle fluid. Castrol’s Axle EPX 80w-90 is a mineral based multipurpose gear oil, suitable for application when oil of API GL5 performance is required."

Is mineral better or worse than synthetic for our use?

 

[VicS]

Any thoughts on this Castol gearbox oil? Castrol 18037160 80W-90 1L Castrol Axle EPX Oil: Amazon.co.uk: Car & Motorbike Quicksilver in tubes is around £40 a litre now. Surely there's a good quality alternative?

Blurb reads: "To prolong the life of your vehicles axles and their components it is vital to keep them topped up with a suitable axle fluid. Castrol’s Axle EPX 80w-90 is a mineral based multipurpose gear oil, suitable for application when oil of API GL5 performance is required."

Is mineral better or worse than synthetic for our use?

It is an automotive oil. It is not likely to be contaminated with water in normal use.
Outboard gear oil is likely to be contaminated with water and we are told that it contains corrosion inhibitors and emulsifiers to combat the effects of water intrusion.

Apart from that if an SAE 80W -90 , GL5 oil is specified it should be suitable. Being a Castrol oil it will be a better choice than most

 

[RichardS]

Any thoughts on this Castol gearbox oil? Castrol 18037160 80W-90 1L Castrol Axle EPX Oil: Amazon.co.uk: Car & Motorbike Quicksilver in tubes is around £40 a litre now. Surely there's a good quality alternative?

Blurb reads: "To prolong the life of your vehicles axles and their components it is vital to keep them topped up with a suitable axle fluid. Castrol’s Axle EPX 80w-90 is a mineral based multipurpose gear oil, suitable for application when oil of API GL5 performance is required."

Is mineral better or worse than synthetic for our use?

View attachment 111694

I would be perfectly happy to use the Castrol oil and would use a fully synthetic GL-5. It's what I use in my saildrives and outboard.

If you can find the exact viscosity from the manual I would try and get as close to that as possible. However, the most common EP grades at 75W or 80W - 90 would be fine.

Richard

 

[Adios]

Outboard gear oil is likely to be contaminated with water and we are told that it contains corrosion inhibitors and emulsifiers to combat the effects of water intrusion.

This is the only thing stopping me. I wonder how true it is though, they do like to exaggerate this sort of thing in marketing

 

[RichardS]

This is the only thing stopping me. I wonder how true it is though, they do like to exaggerate this sort of thing in marketing

I have worked on many off-roaders which need regular diff/gearbox oil changes because water often gets into the oil when wading. They all use standard gear oil even though the oil is usually contaminated when drained. I'm sure that if there were a better oil, the 4WD manufacturers would have latched onto it.

Richard

 

[Skylark]

This is the only thing stopping me. I wonder how true it is though, they do like to exaggerate this sort of thing in marketing

The last 10 years of my career was spent working for a designer and manufacture of niche, automotive gearboxes. I learned a lot of new things about oil additives during that time.
There is usually a very good reason why the manufacturer specifies an oil with certain additives. During the test and validation phase of a new product, one of the many objective tests is likely to have been a fail without the additive. They have invested millions in development, so why ignore their recommendation?
It’s your gearbox so your choice. Some will use an off-the-shelf, near-equivalent and claim, by good fortune, that all is ok.
I have an SD50 saildrive and, notoriously it has a few known issues in service. Quicksilver oil is specified for this box. To save a bit of money, I bought 20 litres and this has lasted >5 years to date. Otherwise, the incremental cost versus popping into Halfords is small beer compared to the overall cost of ownership and gives greater peace of mind. Your choice ?

 

[Adios]

The last 10 years of my career was spent working for a designer and manufacture of niche, automotive gearboxes. I learned a lot of new things about oil additives during that time.
There is usually a very good reason why the manufacturer specifies an oil with certain additives. During the test and validation phase of a new product, one of the many objective tests is likely to have been a fail without the additive. They have invested millions in development, so why ignore their recommendation?
It’s your gearbox so your choice. Some will use an off-the-shelf, near-equivalent and claim, by good fortune, that all is ok.
I have an SD50 saildrive and, notoriously it has a few known issues in service. Quicksilver oil is specified for this box. To save a bit of money, I bought 20 litres and this has lasted >5 years to date. Otherwise, the incremental cost versus popping into Halfords is small beer compared to the overall cost of ownership and gives greater peace of mind. Your choice ?

I'm with you on not halfords hence looking for a high quality alternative. Seems such a rip off if its just the additive that is different i'll be paying £24 a litre as i found the quicksilver vs £8 i can find the castol, makes the additive cost twice as much as the oil. Hey ho, captive audience. Having a boat is like holidaying in centreparcs, they can charge as much as they like once you enter.

I've managed to find a new old stock 2 stroke tohatsu which I'm going to cherish so I'll fork out on the quicksilver

 

[Skylark]

Why not Halfords? If the engine/gearbox manufacture quotes a viscosity and API spec and Halfords brand meets them, I would. My point is that the engine/gearbox manufacture has specified an oil with an additive. That suggests need. Unless you know the reason for the additive, you can’t make a risk assessment to see if your use and duty cycle is likely to see those conditions.

 

[Adios]

Why not Halfords? If the engine/gearbox manufacture quotes a viscosity and API spec and Halfords brand meets them, I would.

Oil is a natural product of varying qualities. Its not all the same. A budget brand will source from a budget source. I think I've damaged my long lived car by skimping and using Mannol oil. I had my doubts when I got it, it smells of nothing. My previous oil had a lovely rich smell. I've gone back to it.

My point is that the engine/gearbox manufacture has specified an oil with an additive. That suggests need. Unless you know the reason for the additive, you can’t make a risk assessment to see if your use and duty cycle is likely to see those conditions.

As I say i'll begrudgingly shell out for the one with the expensive additive. For the amount it uses its not a huge difference. Actually though there is nothing in the engine manual about using a specific brand or additives. But if there is a genuinely better option I'll take it.