Engine oil

Posted by Bill Butterworth On 2015/6/26 19:24:50

Have a 1940 356 engine. Cruising speed oil pressure runs 40+lbs. At hot idle pressure drops to 20+ lbs. using straight 30 wt oil with 1 qt. Rislone to help keep passages clean (engine sat for many years). Want to go to 15-40 wt. with 1 qt Rislone to keep idle oil pressure up. Heard that the Shell Rotila sp? oil has extra additives which is good for these old engines. Can't get the Shell Rotila here but can get Castrol Tection Extra 15-40 wt. which also has the extra additives. Both these oils are used in diesel engines. I suppose this is a good thing as Diesal engine oil has to handle much harsher conditions that gasoline engines. Am I going in the right direction?
Thanks