The Quick Reference Guide:
0) Oil HP Boost:
- An oil change boosts the stock HP by 5%.
- The 5% HP boost lasts for 200 km.
- From 200 km to 300 km after the oil change the 5% HP boost drops linearly 1% per km (i.e. 1% of the total HP gained from the boost).
- The 5% HP boost does apply to whatever the current HP of the car is: so if power tuning upgrades have been installed on the car these will also receive a 5% boost.
1) Rigidity Deterioration:
- The rigidity ‘begins to deteriorate’ at 500 km and ‘rigidity restoration is recommended’ at 19,500 km.
- Rigidity has no influence on HP.
2) Oil Deterioration:
- The oil ‘begins to deteriorate’ at 5,000 km (which also activates the oil light inside car cockpits and on the racing HUD) and an ‘oil change is recommended’ at around 6,000 km.
- There is a total linear loss of 5% HP while the oil deteriorates over the 1000 km.
- Once the oil has fully deteriorated, there is no more HP loss due to bad oil.t
- An oil change resets the oil indicator’s ‘odometer’.
- Maintaining a good oil status does not slow down or prevent the engine deterioration.
3) Engine Deterioration:
- The engine begins to deteriorate at 5,300 km and an ‘engine overhaul is recommended’ at 10,300 km.
- The engine deterioration continues after the recommended overhaul light turns red (unlike with oil deterioration) so that there is continued HP loss until 15,300 km.
- There is a total linear loss of 5% HP while the engine deteriorates over the 10,000 km.
- The engine overhaul fully restores the engine deterioration ‘odometer’, fully restores the oil’s ‘odometer’, and gives an oil change HP boost.
- The oil deterioration and engine deterioration can overlap (e.g. from 5300 km to 6000 km on the odometer when no oil change or engine overhaul have been performed on a car).
4) Permanent High Mileage Deterioration:
- There is a hidden high mileage HP loss that begins around 10,000 km, but may not be visible until about 15,000 km due to the low deterioration rate and PD’s HP rounding issues.
- The high mileage HP loss is very difficult to calculate due to the lack of used cars like in GT5 and due to the fact that the loss may be as low as 3 or 5 % HP over a few hundred thousand kilometers: e.g. with the Red Bull 2011 Prototype, even with its massive amount of HP (meaning changes happen quicker), the deterioration is only 1 hp every 2806.8 km.
- Current estimates are that a 3% loss would happen at around 130,000 km; a 5% loss would happen at around 210,000 km.
- Cars with less HP will drop HP much less evidently and the issue with the way PD rounds HP makes accurate predictions exceptionally tedious.
- The high mileage HP loss has no indicator light in GT Auto because this HP is a permanent loss, unlike the oil deterioration and engine deterioration HP losses which can always be fully restored.
- The loss is permanent: unless PD releases Car Restore Tickets that reset mileage to zero in the future like they did in GT5.
- This loss is unlikely to impact most players since there are no more used cars and most players are unlikely to put 10,000+ kilometers on their cars very often. Also every car can be purchased new besides Anniversary Edition cars.