I have been told by renault sport, that they use 5w 40 in their rally and cup racing cars. This is the oil that gets recommended for my clio 182 sport.
The only prob is that the oil is fully syn, and most old cars with high miles dont run to well on fully syn.
Also when i came to a 6k oil change, trying the get hold of a decent oil brand was a nightmare.
the oil i needed was elf 5 40w. i found the shell helix 5 40 at the shell garage. i bit on the £££ side 9.99 for 1L.
Other things i have found out, the helix oil 5 40w is the stuff honda recommend for their high reving engines in the Civic type R and S2000.
Seems that 5 40w is for sporty engines.
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