The car is a 96 Camry 6 banger with 150,000 miles and I’m told just now it’s more like 15,000 miles since the last oil change.
Ehh...I’m the type of mechanic so proficient that I do my own oil changes, spark plugs, air-filter, fix flats.
SUPER proficient! Heh-heh.
The Pennzoil yellow bottle conventional oil has a very high level of calcium based, surfactant suitable to breaking down sludge accumulations. Change oil and filter after a shorter running interval. Should take out about 40% of deposits within 2000 miles.
As to using diesel oils cross rated to API-SM for gasoline, the cleaning package may increase oil consumption in the short run. Also the higher zinc / phosphorus could be a problem with catalytic convertors.
If a 10W 40 was listed allowable for the car, my first diesel oil choices would be Valvoline Premium Blue X 5W 40 synthetic or Shell Rotella T5 0W 40 based on cleaning surfactant content.