By buying upgrades or nitrous for the cheapest car while Performing cashglitch, you can transfer them onto the new car that cashglitch gets you. This works, because they game attempts to store your upgrades when turning off the console, but can be exploited by some smart menuing. Cashglitch was found many years ago and implemented into cals' first run submitted back in 2019. But the transfer glitch was completely unknown afaik and i first performed and used it in late 2020. The original post of me finding it can be found here for some additional information: https://www.speedrun.com/top_gear_overdrive/thread/eadhv

I initially called it upgrade glitch but transfer glitch makes more sence since it transfers upgrades and nitrous, nitrous are not an ugrade technically as they're one time use. I've already tried abusing this to get the F40 earlier by buying a ton of nitrous after several races and transfering them but afaik this doesnt happen to save time under any cricumstances in any%.