[James Brown]

keep in mind the W measurement means WINTER or cold viscosity, the 2nd number is the viscosity at 100˚C. So you went from 30 weight to 50 weight at operating temperature. You want good cold flow (lower W number) but good or high hot oil viscosity that meets OEM requirements that the engine was designed to run with. I don't know what year engine/car we are dealing with but the oil either synthetic or dino should match the owners manual requirements. Also, what was changed/fixed by the mechanic. Might want to try the Brad Penn 10W30 oil and see what happens.