My 2000 Ranger with 4.0 motor, and only 45K miles on it, calls for 5W-30 and thats what I've always used. I've had the truck since new. In recent years its been used less than 1500 miles per but I changed the oil every spring, usually. I've now begun to use it on regular basis, having downsized to one car and the truck and am wondering if I should continue with 5W-30 or has Ford back spec'ed it to some other weight? I Recently changed it with Mobil 5000 and MC filter and plan on running that for 5K.