hurro
i had a auto R33 GTS4 aswell non turbo 1993, also stock.
awsome cruisers, nice to drive and very comfortable. i remember 1 day i went for a 5 hour drive just coz i felt like it and only stopped once for petrol and once for a drink
had it for about 6 months and only used normal unleaded fuel and previous owner used normal unleaded aswell. car always ran just fine never broke down or anything
its only a non turbo so just service it regularly (every 7000-10,000Ks) and it'll be just fine.
with the cheap fuel and normal sort of driving you'll get 500Ks per tank easily. i used to get about 380-450Ks but with my kind of driving...
best of luck with it