We used 5w/30 instead of 10w/30 we have a 94 ford taurus wagon and have always used 10w we just put the wrong one on accident is it ok to add more 10w to the car…light is still coming on 
If the light that is coming on is the red light with the oil can on it, it means that the oil pressure is low, not necessarily the oil level. Low oil pressure can be caused by a bad oil pump, a blockage, or an engine that is shot. If the light that is coming on says “oil level low” that’s a different story and you need to add oil to bring it up to the full mark on the dipstick. So first thing to do is to use the dipstick and check the actual oil level. If it is below full, then add a quart at a time to bring it up to the full mark. Mixing a quart of 5w30 with 10w30 isn’t going to hurt anything.
Thank you Bing. It never ceases to amaze me how many people think the “oil light” is an oil level light. Often by the time it comes on, the engine is already damaged.
Have a mechanic check the oil pressure. If the oil pressure gauge shows the oil pressure is ok, the oil pressure sensor could be defective. If the oil pressure gauge shows the oil pressure is not ok, engine repair is necessary.
You are now free to move to another car. No need to bother having a mechanic look at it. It’s worth $400 if it’s free of problems. The oil viscosity is not a problem. Add oil if the oil level is low. When does the light go off?
Most cars don’t have a “low oil light.” All cars have a low oil pressure light. You should be in the habit of checking the oil level on a regular schedule. I would start by checking it every week for a month or two. You can best do this when the engine is cool. (less likely-hood of getting burned by something hot in the engine compartment.) If it is holding steady, you can go to once a month.
The change of oil type will not hurt a thing, but I would suggest using whatever the owner’s manual recommends.
FYI Joseph, All Of Our “Newer” GM Cars Have Both An Oil Pressure Low And An Oil Level Low Warning Light And Warning Chime. (Our Older Fieros Don’t.)
I don’t like “idiot lights” or “idiot chimes” in place of real gauges.
However, our GM cars have both idiot lights and idiot chimes for oil pressure and oil level and both have large oil pressure gauges that actually indicate pressure (not just on / off switch).
Should a light illuminate and a chime sound then one should check the oil pressure gauge and stop the car and check the real oil level gauge (dipstick). The oil level low warning alerts the driver when oil volume is diminished by more than one quart of being full and utilizes a sensor installed in a threaded hole in the side of the vehicle’s oil pan.
The coolant temperature gauges and coolant level warnings are also a nice feature.
I wish that the non-GM cars in our family fleet had this redundancy that is usually found in aircraft. Although I check all our car fluids weekly, my wife drives her car 100 miles per day and likes the extra help the car makes available when she’s out there alone.
CSA
sue–Unfortunately, your post is so unclear as to the sequence of events and what was done that it is very difficult to make sense out of it.
Was the 5w/30 used when the oil light came on, or was it used the last time that the oil was changed?
Was the car warmer than usual, or was the engine warmer than usual?
Did you use the dipstick to determine if the engine needed oil, or did you just decide to start adding oil as a result of the warning light?
Does the engine still need oil, as indicated on the dipstick, and if not, on what are you basing your opinion that it still needs oil?
As the others have already begun to surmise, I suspect that you did not use the dipstick, and that you interpreted the oil pressure warning light to mean that the engine has a low oil level. In reality, that warning light indicates that the oil pump is not supplying adequate oil pressure to the very sensitive bearings. Low oil pressure can result even when the crankcase is full of oil. Did you ever use the dipstick?
It is also possible for a bad oil pressure sensor on the engine to send incorrect signals to the warning light on the dashboard.
Based on how I am attempting to piece your very confusing post together, I am going to take a quantum leap here, even though I could well be wrong:
I believe that your engine has dangerously low oil pressure. This could result from a bad oil pump (unlikely), or it could result from an engine that is very badly worn (from poor maintenance or from many miles on the odometer, but you failed to tell us about maintenance or how many miles are on the odometer), or it could result from a huge amount of sludge in the engine. Sludge builds up when oil is not changed often enough. Is that a possibility?
It is also possible for the oil pressure warning light to come on if the actual level of oil in the crankcase is extremely low–which is the result of not checking the dipstick periodically between oil changes. Is that a possibility?
If the oil level in the engine was not low when you started adding oil, then it is now overfilled, and that is potentially as bad as a very low oil level–no matter what viscosity oil is used.
In regard to the “car is warmer than usual”, if that refers to the temperature gauge on the dashboard showing a higher temperature than usual, it leads me in the direction of dangerously low oil pressure, rather than a bad oil pressure sensor in the engine. If this is the case, then severe engine wear has probably taken place as a result of the low oil pressure.
Although I have a very bad feeling about the prospects for this engine, it is possible that we are all barking up the wrong tree as a result of your way of explaining the situation currently. How about coming back to this thread and posting the information in a more understandable sequence, and by including answers to the questions that I posed?
First check engine oil level before adding more.
If full or close have a mechanic put an oil pressure guage on it and give you the good(sensor) or bad(engine finished) news.
The mechanic check will give piece of mind of break down if that is important.