on my 1997 chevy blazer, the gear column goes 1,2,3 [D] the previous owner said to drve it in third, but when i drive it in overdrive, the RPMs are lower but it seems like it uses more gas. What gear should i drive it in?

 

OD (D) for just about everything. The only time that you should consider dropping down to another gear while driving is if the transmission is hunting a lot. By hunting, I mean shifting in and out of overdrive frequently. Hunting causes a lot of heat buildup in the transmission as well as wear.

It shouldn't use more fuel in overdrive than 3rd...