6.8 bolt for automotive use?

[ET16]

I was working on an exhaust flange on my Mazda MPV and used an M10 6.8 bolt I had on hand. Should I change it out? I don't know metric fasteners that well, but see that 6.8 is not as strong as a typical grade 5 bolt.

 

[Trav]

There is no 6.8 that I am aware of, its either a 4.6, 4.8, 5.8, 8.8, 9.8, 10.9, 12.9.
The ones under 8.8 would be rare so i strongly suspect you have a 8.8 in there and that's fine.

 

[ET16]

Strange. It has "CS 6.8" on the head. I don't know where I got it; it could have been Switzerland.

 

[krismoriah72]

6.8 is a grade 2 bolt. Those will work fine for you. Instead of snapping they will bend or twist. I like Grade 5 for exhaust myself but what you have is fine.

 

[UrS4]

just put in a 8.8 bolt!

 

[A_Harman]

8.8 I think has equivalent tensile strength to Grade 5.
10.9 is equivalent to Grade 8.

 

[Trav]

Originally Posted By: ET16
Strange. It has "CS 6.8" on the head. I don't know where I got it; it could have been Switzerland.

I just googled it, it exist but I never saw one even in Europe. It is not common marking in automotive use, I have seen small metric bolts with no markings that are equal to grade 2-3.
I try to use stainless in exhaust applications if available, Ace hardware has a good selection of metric stainless.

https://sizes.com/tools/bolts_metric_standards.htm