Like all historical documents, factory manual recommendations must be
taken in context. The oils originally specified by brand and type had
very different qualities than oil currently available.
The recommendations are a useful guide, but modern alternatives and
updated user information must be examined.
A perfect example of this is the gear lubricant specified for the
Rover/Triumph 5 speed gear box. The factory manuals specify 90W, which
proved to be disastrous in the North American market.
Detergent packages used during the 70-80s were a concern when the oils
were used for gear lubrication. During that time period the recommended
gear oil for MGB transmissions was a non-detergent racing type oil such
as Valvoline Racing. Currently oil packages have changed dramatically
with the popularity of turbo charged engines, and I have absolutely no
clue what to recommend, but I don't think you would go far wrong by
using a regular 20W 50 non synthetic engine oil.
Kelvin.
Subject: Re: Oil for Overdrive Transmission
Hi CR,
I checked my owners manual and you are quite right. It does recommend
the same oil in the Engine and transmission. It doesn't specify a
difference between OD and non-OD transmissions. I understood John
Esposito to say that his recommendation to use non-detergent 30W applies
only to OD transmissions.
I also noticed that the MG manual recommends 10W/40. I found that
especially interesting because I have understood from several sources
that 10W/40 was not a wise choice at all. Under high heat conditions it
leaves hardened deposits. For that reason, I don't think it is
recommended for turbos and I don't think it's recommended for air cooled
engines.
I understand that it leaves hardened deposits at the end of the piston
travel and as the rod bearings wear the piston travel increases and the
rings hit the deposits. The rings can crack and lodge the piston in the
cylinder and blow the engine.
After using Kendall 10W/40 in a 2.3L Ford for years it started to knock
and about 2 weeks later a piston seized in the cylinder, snapped the
rod and pushed it through the block. It failed exactly as predicted in
the literature.
Whether it was caused by the 10W/40, I can't say for sure. But it was
enough for me. I wouldn't use 10W/40 in anything.
I would view any recommendation to use 10W/40 with a bit a skepticism.
Perhaps when the manual was written they were not yet aware of the
problems with long term use of certain lubricants.
:-)
Don Malling
Charles & Peggy Robinson wrote:
> He's full of beans. I've been running Castrol GTX 20W-50 oil in
both
> my MGB engines and OD trannies for over 15 years, no problems. I do
not
> understand why people want to ignore the owner's manual which clearly
> states that you should run the same dino oil in the tranny as you use
in
> the engine.
>
> Cheers,
>
> CR
>
> Don Malling wrote:
>
>> According to John Esposito www.quantumechanics.com, only 30W
>> non-detergent motor oil should be used in an OD transmission. John
>> said that deteregent motor oil will foam in the transmission and will
>> not work well with the OD. I can't remember the details of why the
>> foaming was not good for the OD.
>>
>> Don Malling
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