Tried that, many times. Clown cars go down very fast. I found it better to have a sniper in it, keeping distance.
Funny, you mentioning shock troops. Just yesterday, I had two squads of shockers attack one upgraded panzergrenadier squad. I came in close, and had to retreat. Maybe he got lucky? He still had 4 men in the squad left, only the squad health was down low. I know shockers work for the most part, but only effective when vetted...
We have had some good results with Penals, but we end up being overrun by the mass of grenadiers...
Shock troopers easily win a 1v1 with pgrens if no nades are thrown. What do you mean by "upgraded"? Shrecks or g43's
Either way 2 shocks should wreck the pgrens. Maybe you had lowhealth and he was in green cover