UK Car Repair: MGB, recommended lubricant, oil formulations

Question
QUESTION: I am confused by the "new" oil formulations. I currently use CASTROL 20-50. My car has over 60K so do I continue with the CASTRO or what do you suggest. I have heard that REDLINE synthetic is a recommended lubricant.

ANSWER: All engine oils have to meet the same specification, the biggest difference between oils is the packaging. You do not need to use synthetic, you do though, need to do regular changes.  Multi grade oils are a compromise, single viscosity oils are much better. Change oil with the season temperature, using perhaps a 30W in summer and a 10W in winter.

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QUESTION: What about the new lower zinc in the new oil formulation which I understand can cause rapid wear on the cam & lifters?  Every publication about brit cars recommend a 20-50 grade? MGB '75

Answer
The specifications of all manufacturers have to meet the same standard.  I doubt if any additives would cause "rapid wear" and other than the Oil companies -who do extensive testing- who would know such a thing?  20/50 is recommended as it fits virtually all temperature conditions in central Europe, so it is a catch all, the fact is if you know the temp range in your area you can make a better choice through the seasons.