Is it OK to use wrong moto oil?

Yes, for a while. The world and your engine will not come to an end.

dont worry about it just run it as normal. dont even change it wont hurt a thing. If anything you helped the motor a bit by running a 30 which is thicker than the 20 thus coating the engine parts better and longer. They only use the 20 to save a bit on fuel. and that first number only applies when the temperature gets below freezing..

Absolutely NOT ok. Anybody who says it is, isn't up to date on the latest oil technology. Read this article on what can happen with the wrong viscosity. This ain't the '60's anymore. Today's engines rely on oil pressure and specific viscosity to run camshaft phasers, high pressure gas pumps, and to cool turbos

http://ricksfreeautorepairadvice.com/motor-oil-vis...

What's the year of your truck?

Bernadette needs to go back to school concerning engine oil viscosity. 40 weight is not recommended by anybody. The lower the viscosity number the freer flowing the oil is.

about the only thing you might notice is a slight change in gas mileage. aside form that, nothing at all. look in the owners manual on the recommended oils and ill bet that 5w30 is on the list.

Because older models use thicker oil which is usually 30 weight and newer models use lighter oil which is 40. Just make sure to use correct oil

http://www.scribd.com/doc/48798088/T-TT-0005-10

No big deal.