What are 4.8 / 8.8 / 10.8 / [and similar] bolts?

These are strength designations for metric bolts. DSMs, being primarily Mitsubishi cars, use metric fasteners.

Metric bolt strength is designated by 2 numbers separated by a decimal. The first number is the minimum tensile ultimate strength: the resistance to fracturing, given in megaPascals (MPa). The second number is the minimum tensile yield strength: the resistance to deformation, and is rated as a percentage of the first number. Thus, a 10.8 bolt has a 10 MPa ultimate strength, and a yield strength of 0.8 (80%) of that number (= 8 MPa). Generally, the higher the better.

For more detail on the differences between ultimate and yield strength try this chapter of the material sciences guide at tpub.com.

For a table of typical fastener grades, try here.