If your primary oil is low, there are a few things you can do to check. One is to check the dipstick. Most engines have a mark on the dipstick that indicates the minimum amount of oil that should be in the engine. If the oil level is below this mark, then your primary oil is low. Another way to check is to look at the Oil Pressure Warning Light on your dash. If this light comes on, it means that your engine does not have enough oil pressure, which could be caused by low oil levels. Finally, you can listen for any unusual noises coming from your engine. If you hear knocking or ticking, it could be a sign that your engine is low on oil.