what is the condition of tyres. If it was parked for very long time un attended check for any fractures in tyres.
IF ALL IS GOOD you need correct tyre pressure in all 4 and wheel balancing.
IF there are fractures in tyres, you shall replace the same size in A/T ( all terrain ) grade
3400 petrol V6 will be good for 7 km to a litre in city & 9 over the highways.
for 4x4 off roading it will be real mean fuel guzzler
oil grade you can comfortably use 5W-30, 10W-30 of any known brand, with oil filter change it will take 5.6 litres & without oil filter change it will take 5.3 liters
change interval shall be 7000+ kms.
All the best & Good luck