I always use EP90 to the API-GL4 spec.
20w50 is considered by some to give better operation of the overdrive, and I
understand Laycock specified something in the region of 30 weight for the
overdrive. Obviously, as the gearbox and overdrive share the same oil, there
has to be a compromise.
Interestingly, all of the BMC vehicles I have worked on (MGB, Midget) have
had the same oil specified for transmission and engine.
If you don't have overdrive, there is no conflict of interest - just use
EP90.
> Kirk's transmission mechanic recommended 20W50 motor oil for
> the tranny
> instead of hypoid gear oil? Somehow, 20W50 motor oil doesn't
> seem like a
> suitable replacement for 90W or multi-weight hypoid gear oil.
>
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/ \ William Davies
/ \ Total Triumph Enthusiast
__ __________________ __
/ \ ______ ______ / \ 1959 Herald 948 Coupé Y128
\__/ \ || / \__/ 1959 Herald 948 Coupé
| A \____||____/ A | 1959 Herald 948 Saloon
| = H H = | 1960 Herald 948 Saloon Export
=====U==============U===== 1961 Herald 'S'
\________________________/ 1964 Herald 1200 Saloon
| | | | 1970 Spitfire MkIII
|_| |_| 1973 Spitfire MkIV
1959 Standard Atlas Pickup
|