772ed185_Grand_Theft_Wiki__the_GTA_wiki__Description
[Ability] Fire-proof [Code] FP [Description] 
This is the least valuable of all special properties available. A car that is bestowed with a fire proofing won't catch on fire from any flames surrounding the car (for example, from a Flame Thrower or Molotovs). However plain fire proofing cars are extremely rare, and isn't very helpful otherwise since it is rare for a vehicle to catch on fire.
Special Vehicles - Grand Theft Wiki, the GTA wiki