I have an 86 Samurai with 116K that's used for short trips around town and light off-roading in the desert and up north in the woods. It sees 3K a year, I've been using dino 10w-30 and NAPA GOLD filters on a yearly OCI. The oil gets pretty black and it used a quart in 3K. I just upgraded to a Weber carb from a less than optimal Toyota carb conversion that was done years ago and always ran a bit rich. Just changed the valve cover gasket and it's clean inside. I've got Pennzoil HM 5w-30 on deck for the next change probably in January. Is once a year OK?