Exactly - I have a guy who comes into the shop every summer on his vacation and tries to insist I put Rotella 15w40 into his 2008 Pontiac G6!! Give me a break - I refused and turns out he uses it because he gets it for free since he handles fleet service for his company. He's just asking for trouble when the car needs 5w30. There are some older and higher mileage vehicles I switch to 5w30 vs. 5w20 after talking to the owners to reduce some consumption but certainly not recommended unless you have an issue.