Kelvin,
An owner's manual is not a history book. It's a recommendation by
the manufacturer's engineers, based on tests that they ran before they
published the manual. These tests were run using the lubricants of the
time. Lubricants and their additives have improved over the years.
Where history comes in is the publishing of opinions by various "gurus"
as the years pass. So much of this is published that it takes on the
appearance of fact. Here's an example: John Twist maintains that
overdrives don't cut wear and increase gas mileage. He won't budge off
of this opinion despite evidence to the contrary. Hence, there are
Twist followers who believe ODs are not desirable.
I know of no evidence that multi-viscosity detergent oil has harmed
an overdrive transmission. Until I see some, I'm going to stay with the
factory recommendation.
I do get a kick out of your last paragraph. One the one hand you say
you don't have a clue as to what to recommned. Then you go ahead and
make a recommendation. ;^)
Cheers,
CR
P. S,: How about some more info on the Triumph/Rover gearbox problem?
Dodd, Kelvin wrote:
> Like all historical documents, factory manual recommendations must be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.
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