Upgrades are done in the Garage: pick a car, open its card, and you'll see four parts. Levels are stored per car, not per account — buy a second car and it starts stock.
Every next level costs a fixed multiple of the previous one:
There is no level cap — only your balance stops you. Engine and turbo cost more because they give raw power; tyres and transmission are cheaper because they give control rather than seconds outright.
Starts at level 1. Every level above the first adds +15% acceleration in every gear. It works all the time, from launch to top speed.
Starts at level 0, so turbo has to be fitted from scratch. Every level adds +25% acceleration — the strongest multiplier in the game, which is exactly why it gets expensive fast.
Engine and turbo multiply together. Engine 3 with turbo 2 gives 1.30 × 1.50 = 1.95 — nearly double the stock acceleration.
Starts at level 1. Every level gives +8% grip, which affects two things:
Tyres also raise the wheelspin threshold at launch: 6,600 rpm +80 per level. With upgraded tyres you can hold higher revs on the line without going up in smoke.
Starts at level 1. It adds no power — it forgives mistakes:
It's the most useful part for anyone still learning the gearbox.
Your rival mirrors your levels ±1 and runs the same power formula. The opponent pool is also matched to the actual run time of your upgraded car, not to its sticker price. So upgrading doesn't make races free — it lifts both cars and leaves the advantage to whoever launches better and shifts cleaner.
A trade-in returns half of what you actually spent on upgrades. The other half stays with the car — deliberately, otherwise the garage would work as an interest-free money store.