oil weight

I just purchased an 94 nissan pickup 4 cylinder. What weight oil do I use?

10w 30.

No you want to use 5w 30 weight oil. This weight oil has been recommended in Nissan's from at least 1984 that i know of. This weight oil is still recommend to this day.

I have a 93 and there is a sticker on the underside of the hood that says 5w30 is preferred ONLY if the temperature in your area gets below 0 degrees, otherwise 10w30 is recommended. I believe this is also in the manual that comes with the truck.

ive got a 96 xe 4x4 and ive been runnin shell rotella t 15 40 motor oil as soon as i started useing it my gas milage went up

I run 5W30 fully synthetic. I'm in Nova Scotia where winter temperatures easily hit -10ºC.