After long time of hiding secrets of various Spike cars,he told that he works as car mechanic.

''Spike,did you got another car again ?''
''No Rarity''
''So from where did you got that 400R ?''
''Well...i think that's time to tell you something''
''hm ?''
''im...im..damn im car mechanic,and i just use them before i give them to clients''
''Spike..why you was hiding that before me ?''
''i..i was thinking that you will stop loving me''
''Spike...''
''yes,i know that im bad...''
''I still love you Spike,nothing can change that,Darling''

Sources :
Background : https://www.deviantart.com/teaganlouise/art/MLPFiM-Night-background-257051797
Spike and Rarity : https://www.deviantart.com/georgegarza01/art/Sparity-Remember-This-782363342
Nissan : official Skyline 400r brochure + neon effect by me^{^}