Formula shell would be the budget full-syn oil, since shell's got Rotella line of full syn oil above it.
Mobil 1 should be a better bet (and Mobile 1 EP even better again), having said that, if you do regular oil changes, at 35.24 per 5 litre.. .
You can't really go wrong, I mean its even cheaper than Nulon and Castrol edge at that price.
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