Consequences of wrong grade gearbox oil?

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At a guess I'd say it would affect your gearbox and the way it functions. Why else would the manufacturer bother to give a specific grade of oil to use on the gearbox?
 
Garages will sometimes use different one's, id of checked before, not sure you could make them change it for what it says in your handbook.
 
this is a personal bugbear of mine.

Half of the time, the "recommended" oil for the car is just an excuse to push somebodys products.

Take my volvo for example - they recommend the car be used with a grade of oil and to use castrol - but castrol don't sell that grade of oil to the general public. The full name of the product Volvo recommends is Castrol SLX Professional Longtec For Volvo Engines

Only availabe from ... guess what .. your local volvo dealer for something stupid like £40 a litre.

In reality of course, people have substituted the oil for other fully synthetic castrol oils of similar ratings (volvo say 0W30 A5/B5) but Castrol Edge 0W30 A3/B4 despite not being A5/B5 is absolutely fine.

I would speak to a specialist independant on the telephone somewhere and see what they would use. Likewise consult owners forums.

It may well be the case that grade of oil is fine too.
 
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75W-85 and 75W-90 will be very similar, I would be more interested in what spec it was versus what is recommended.

MrLOL said:
this is a personal bugbear of mine.

Half of the time, the "recommended" oil for the car is just an excuse to push somebodys products.

Take my volvo for example - they recommend the car be used with a grade of oil and to use castrol - but castrol don't sell that grade of oil to the general public. The full name of the product Volvo recommends is Castrol SLX Professional Longtec For Volvo Engines

Only availabe from ... guess what .. your local volvo dealer for something stupid like £40 a litre.

In reality of course, people have substituted the oil for other fully synthetic castrol oils of similar ratings (volvo say 0W30 A5/B5) but Castrol Edge 0W30 A3/B4 despite not being A5/B5 is absolutely fine.

I would speak to a specialist independant on the telephone somewhere and see what they would use. Likewise consult owners forums.

It may well be the case that grade of oil is fine too.
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in that particular example , the Volvo oil is the only oil that Volvo recommend for extended drain servicing.
 
frakker said:
I've posted a similar query on the Fiat Forums, just waiting for someone to reply - I know you lot are a lot quicker on the 'reply' button!

I have had a look on the Opie Oils website, and that too seems to recommend using 75w-85.
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Opie will recommend the most expensive tbh. For my car, it's about £9 per litre from Honda, the same stuff is sold by Land Rover for about 1/3 that

If it 'feels' ok now, then just stick with it
 
Surprising how many love some 10w40 semi-synth in them. We had a problematic Renault box and spoke to renault technical who stated 'oh that's a common issue, its slight play in the input bearing, just use engine oil it will be perfect.' And it was.
 
10W-40 is similar viscosity to 75W-90 so it kind of makes sense. The additives in engine oils are usually fine for normal gearboxes too
 
Carlube do sell a 75W-90 that is GL-5 rated

http://www.eurocarparts.com/ecp/p/c...oils/manual-transmission-fluids/?522770532&0&

that appeasr to be what they've used :/

The GL-4 rated product is a different one.

http://www.eurocarparts.com/ecp/p/c...oils/manual-transmission-fluids/?522770502&0&

The difference in GL-4 and GL-5 is that GL-4 gear lubes have half the extreme pressure additives of GL-5. Because the gear types in manual transmissions do not necessitate the use of GL-5 gear lube, GL-4 is the correct recommendation called for by most OEM’s when gear lube is required.
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http://www.amsoil.com/articlespr/2007/article_gearoilbasics.aspx

Don't see how it can be both GL-4 and GL-5 personally. Simon's the best person to answer that.
 
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MrLOL said:
Don't see how it can be both GL-4 and GL-5 personally. Simon's the best person to answer that.
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Well I know that Amsoil ATF being higher grade than Dextron III and II can be used as a substitute for either, maybe because GL-5 is better than GL-4 it can be used as a substitute and the oil in question is a higher standard than both so covers both spec like the Amsoil does?
 
amsoil say that GL-4 has half the extreme pressure additives of GL-5.

Fiat specialist says not to use GL-5 because the gearbox is soft. I conclude from that that having more of those high pressure additives is a bad thing.

Can't see how it can have both ?
 
I'm not very involved in gear oils but GL-5 oil will have more EP additives than GL-4 which will mean a potential for more yellow metal corrosion as the sulphur will attack the bronzed syncros etc.

You can't have an oil thats 75W-85 and 75W-90. Nor GL-4 and GL-5, GL-5 is more typical of differential oils.

Dexron III is backward compatible with Dexron II applications
 
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