Leave it in AUTO for 99.999% of all needs. 4 lo only needed in rock crawling/tight trails. Gas mileage in 4 lo is probably in the single digits. 4 hi only needed for higher speed off roading....ie open trails, gravel, sand. Auto for anything on pavement. The computer switches drive wheels as needed with in milli- seconds. Best gas mileage for 4 wheel drive in Auto. Also, when the "slip" is occurring, it is actually the VDC kicking in, thus applying brakes to the "slipping" wheels and computerly guiding you to safety. I've tried experimenting in many conditions and really like the VDC. It is sometimes overbearing...but when it is slick....needed. I went one Colorado snow storm with it off just to see.....it's like you're a kid again, sliding the rear end out, etc.... BUT..when you're oversteering with this big of a vehicle it sometimes becomes too late for correction because of the sheer mass of this beast. My old RX-7 was fun, this can get dangerous. With the VDC on it usually allows for a little rear end slide, then holds that glide until forward momentum kicks in. Much better than my wifes Audi which doesn't even allow for any fun. LOL