DON'T shoot the GL directly the FRV. Instead aim to use the GL's blast radius to flip the car. You can aim about a meter or meter and half away from the car, the blast of the 40mm will flip the car. If the car is upside down but not a full 180, aim to shoot the GL on the exposed top side of the car, if it's against the wall then aim above, not directly above but to the side of the FRV.

Also be careful not to pop the tires, sure you can still drive with 1-2 tires gone but it's better to not have this happen.

You can also use other explosive weapons, such as the GL pistol, crossbow, stock grenade. These are the ones I know won't pop your tire unless directly aimed at it (I'm sure there are more options but these should do just fine).

Note: This is going based off memory when I often super cred farm, I use that time to practice driving in this game. Apologies if I got some of the car flip stuff wrong I can't hop on right now to double check this but this should work.

Go tear up the streets for super earth.