When you acquire more cars get rid of the average ones. Concentrate on building a top car, then invest in a better one after it has been maxed out.
Challenges
Complete challenges as often as possible to win wrenches, which are used to upgrade your car. Challenges can also be simulated and not actually played. Even if you lose, you still receive a prize.
Oil
Change your oil before exiting the game. The process requires two hours to complete and is best started when you have to exit the game for awhile.
Perfect starts
Practice getting a perfect starts for an additional advantage. You do not need to always be in the green with the pedal; you can also get slightly ahead before the timer reaches zero, then allow it to fall back to the correct position.
Shifting
In the races where you must time your gear changes perfectly, concentrate on the indicator. As soon as the line gets close to red, switch gears.
Upgrades
Purchase the power upgrades first to win races easier. Then, keep everything balanced for a well performing car.
Cars...