Thanks for that. Commonly, the only stainless used in industry is 330 and 440. The other types of stainless have specific uses and would not be suitable for fasteners for autos. Of course, always check the grade of bolt you buy. You can tell what grade the bolt is by the markings on the head. The grade 5 bolt will have 3 lines engraved into the head which run radially out from the centre. The grade 8 will have 6 lines. More lines = stronger bolt. Grades below 5 are essentially junk and shouldn't be used on anything - they have no lines.
Metric bolts run from ISO grade 4.6 to 12.9. You would be looking for a grade 9.8 or higher. The grade numbers are actually engraved on the head of the bolt.
