Hello S-Type,
The reasoning behind said statement is that in general terms, less expensive mineral based 20/50 oils may be less likely to resist shear forces over a longer period. Also, dispersant and detergent life may be less than that of premium lubricants.
However, to be certain of greater lubricant longevity, check the specification given for the oil on the container or directly with the manufacturer.
Certainly, Morris Lubricants has a help line and can assist with specific enquiries about many aspects of their lubricants.
From experience, I can say that on the occasions that I have had to resort to using whatever 20/50 I can get my hands on for top-ups, no ill effects have been encountered. But when that has occurred, it has been my policy to change oil and filter at the earliest convenience in order to obtain more reliable service and change intervals.
If modern engines still used 20/50 we'd all be buying the synthetic version, but as current demand for such a product is relatively low, none is on general sale. If it were, at today's demand levels, we'd be looking towards a three-figure sum per gallon.
Therefore, we are currently using cheaper and to some extent, less capable products and as a result need to change our vehicle's lubricants more often.
I can be contacted directly at
fuzztownshend@yahoo.co.uk, should you wish for any further info/clarification. You'll probably get a swifter response.
I enjoyed your post about current MoT legislation. We live in interesting times indeed.
All the best,
Fuzz
