If you're that paranoid, make your attached garage out of concrete or blockwall + a metal door going in, then fire can't get out of the garage.

I have no fear at all parking a diesel car in the garage. You're more likely to have the house catch fire from a meteor impact or lightning.

Gassers....I just don't like them period. So nothing to worry about there.

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)