10W-30 was recommended by GM
10W-30, 10W-40, 15W-30, 15W-40 would be OK
bi-annual - every two years
semi-annual - twice a year
Factory recommendation: 2,000 miles
I usually change mine annually (once a year, in the Fall), unless I travel more than 2,000 miles in a year.
5 qts plus capacity of oil filter (if installed - 1qt or 2qt, usually)
Oil filter changed every 2,000 miles
There were many styles (brands/sizes/years) of filters that were used on 235s.
Do you have an owners manual and/or a Shop Manual?
