Mayhem 3D

I'm just going to copy/paste my solution from the 100% completion achievement in this game. Obviously for this, you will get it on the way to 100%.

Issue 1: Rules of the Road - 4 events for 12 stars.
Issue 2: Dead Man at the Gorge - 4 events for 12 stars.
Issue 3: Date with Disaster - 5 events for 15 stars.
Issue 4: Blue Ribbon Brawl - 5 events for 15 stars.
Issue 5: Toro! Toro! Toro! - 5 events for 15 stars.
Issue 6: Mixed up Mayhem - 5 events for 15 stars.
Issue 7: Unleash the Beasts - 6 events for 18 stars.
Issue 8: A New Level of Mayhem - 6 events for 18 stars.
Issue 9: The Final Standoff - 6 events for 18 stars.
Issue 10: End of the Road (no playable races)

A total of 46 races. I found that I used a monster truck for Demolition Derby and Domination. Whereas for Banger and Elimination races I used a muscle car and used the handbrake to take sharp turns. Also a pickup truck is great for the challenges of pushing cars over the edge.

Good Luck!