Not sure but Extreme races are not below level 20.
Think you mean expert level races which are level 15+
OP just do the same races over and over. The highest you have unlocked
With an over powered car.
Using the GT matrix from these GTplanets forums will show you which pays the highest XP.
Why is everyone in such a hurry? Everyone complains about how bad the Bobs are, but they continue to stick a 0 level Bob in 30+ level races so they end up with a 40 level Bob with very little experience. Is it any wonder that they are bouncing off the guardrails all over the place. It's like taking a 12 year old kid out of a 25hp kart and tossing him into a F1 ride! I'll take a 30 lvl Bob with over 50% exp meter over a 40 lvl Bob with less than 25% exp anyday.