A little trick that I use to save my engine a bit is to only do as many of the races as you have to in order to win the series. For example, in a 10 race series, if you win the first 6 or 7 races you can sometimes win the series on those points alone. That way you can get the money, and car, and change your oil before it kills you. You can also go back and individually win the last few races for the %, and change oil after everyone if you please.