If you can open the hood, check the oil, and take the oil cap off, you might fix your problem by spending less than $5.
Assuming your vehicle has an oil pressure gage, 40 to 60 pounds of pressure is a satisfactory reading. If the reading varies from less than 5 pounds to about 40 pounds often, you're engine is probably just low of oil. Check the engines dip stick to verify the oil level is to the full mark.
It can be difficult to get an accurate oil reading of some vehicles, especially when they're hot. The best time to get an accurate oil reading is after the vehicle has been parked all night. You probably won't even have to wipe the dip stick then. Just pull it out and look at it.
If the dip stick still indicates full, the next thing I'd do, is add at least an additional half a quart of oil to the crank case. Then take the vehicle for a test drive. If the oil pressure gage is reading like it's suppose to without the fluctuations, you've probably verified the engine has the wrong dip stick in it. (Whether someone lost a dip stick and bought the wrong replacement, or it was a factory error, mission accomplished).
If step 3 didn't take care of the fluctuations of oil pressure, add a pint or quart of upper cylinder cleaner to your engines oil. It may take 5 to 50 miles or more of driving before you see consistent results.
When you're oil pressure gage is reading zero, put a bottle of engine flush or prep into the engine. Read the directions first. The kind of flush, that allows up to 100 miles or more of driving before an oil change, may be your best option. Some engine oil flushes only recommend allowing the engine for 5 minutes of idling right before a mandatory oil change.
