@finch
Surly ZIC A 10W40, API SM can withstand to any hash condition too
and to understand differance study API chart of Base oil Grouping
and understand it
ZIC XQ , Mobil 1 are the synthetic oil produced from Group IV
and ZIC A is produced from Group III
Both are Synthetic but Group IV has plus supriority compare to Group III
API Base Oil Classification
Group Vis. Index Saturates Sulfur Other
I 80 - 120 <90% and/or ≥0.03% -[LEFT]
[LEFT]II 80 - 120 ≥90% and <0.03% -[/LEFT]
III >120 ≥90% and <0.03% -
IV PAO (Poly Alpha Olefin)
V Everything Else
[/LEFT]