I swear we just had this discussion in another thread...
Figure this into your equation:
I hit 40.0 DS at 10 am TCT Dec 28, 2018 on a parkland 100-lap race... since that time, I have only raced 100-lap docks races using a fully upgraded (Turbo 3, Long, Tarmac) Ferrari 458.
Through eighteen 100-lap docks races my DS has not changed. So I am gaining less than 0.1 / 18 DS per 100-lap docks. One of the reasons the DS gain formula is difficult to figure out is the fact that I have no idea what I am gaining from each race. It appears I have gained nothing, but we can be somewhat safe in assuming a gain of 0.005 or so from each race (I expect to gain 0.1 in the next race or two, but I'm not sure).
When I was in the 30's and worked at Guy's 10* mech shop (so +50% skill gain), it took 11 docks races to gain 0.1 and something around 50 speedways. I think I deleted the table I was making, unfortunately.
Anyway, the possible variables include driver class, car/car class/upgrades, track, time, laps, official vs unofficial, starting DS (assume it's something like hunting with diminishing returns), racing points earned (lifetime). My guess is the formula is exponential or logarithmic, as most Torn formulas are, so a flat DS per time as you suggest is unlikely.
| Race | Start DS | End DS | Race |
| 0 | 39.9 | 40.0 | You came 2nd in the Parkland race. Your best lap was 02:39:22. [View] 2018/12/28 10:06:04 AM |
| 1 | 40.0 | 40.0 | You came 1st in the Docks race. Your best lap was 02:49:59. [View] 2018/12/28 6:01:05 PM |
| 2 | 40.0 | 40.0 | You came 1st in the Docks race. Your best lap was 02:50:20. [View] 2018/12/28 11:17:03 PM |
| 3 | 40.0 | 40.0 | You came 1st in the Docks race. Your best lap was 02:45:25. [View] 2018/12/29 4:29:04 AM |
| 4 | 40.0 | 40.0 | You came 2nd in the Docks race. Your best lap was 02:48:96. [View] 2018/12/29 9:39:05 AM |
| 5 | 40.0 | 40.0 | You came 1st in the Docks race. Your best lap was 02:50:62. [View] 2018/12/29 7:44:03 PM |
| 6 | 40.0 | 40.0 | You came 1st in the Docks race. Your best lap was 02:50:51. [View] 2018/12/30 12:44:03 AM |
| 7 | 40.0 | 40.0 | You came 1st in the Docks race. Your best lap was 02:50:14. [View] 2018/12/30 5:44:04 AM |
| 8 | 40.0 | 40.0 | You came 6th in the Docks race. Your best lap was 02:50:80. [View] 2018/12/30 10:58:04 AM |
| 9 | 40.0 | 40.0 | You came 1st in the Docks race. Your best lap was 02:50:56. [View] 2018/12/30 7:10:04 PM |
| 10 | 40.0 | 40.0 | You came 1st in the Docks race. Your best lap was 02:50:61. [View] 2018/12/31 12:11:04 AM |
| 11 | 40.0 | 40.0 | You came 3rd in the Docks race. Your best lap was 02:43:00. [View] 2018/12/31 5:20:04 AM |
| 12 | 40.0 | 40.0 | You came 1st in the Docks race. Your best lap was 02:50:64. [View] 2018/12/31 10:22:04 AM |
| 13 | 40.0 | 40.0 | You came 2nd in the Docks race. Your best lap was 02:48:00. [View] 2018/12/31 7:12:04 PM |
| 14 | 40.0 | 40.0 | You came 3rd in the Docks race. Your best lap was 02:49:71. [View] 2019/01/01 12:31:04 AM |
| 15 | 40.0 | 40.0 | You came 3rd in the Docks race. Your best lap was 02:47:42. [View] 2019/01/01 5:40:04 AM |
| 16 | 40.0 | 40.0 | You came 6th in the Docks race. Your best lap was 02:50:10. [View] 2019/01/01 11:04:04 AM |
| 17 | 40.0 | 40.0 | You came 3rd in the Docks race. Your best lap was 02:50:70. [View] 2019/01/01 8:21:04 PM |
| 18 | 40.0 | 40.0 | You came 2nd in the Docks race. Your best lap was 02:50:48. [View] 2019/01/02 1:26:04 AM |