Using the wrong motor oil - dangers

So I’ve been driving a 1999 Ford Contour for the last 3+ months. The car was given to me after my previous car died.

While driving home from work a few days ago, I took a corner and saw my Oil light flash on, then back off again. It did this each time I rounded a corner. Well crap, I guessed that meant that I was very low on oil, but not completely out. I pulled into a grocery store parking lot and shut off the engine.

From my trunk, I retrieved the two quarts of 10w30 motor oil that I had salvaged from the trunk of my old car before sending it to the junkyard, and dumped them into my engine. Then I went into the store and bought a couple more quarts of 10w30 and added them as well. After that, my dipstick showed my oil was full.

The potential problem is that I don’t know if 10w30 is the correct oil for the Contour’s engine. There was no owner’s manual in the glove box. Given that I was apparently nearly out of oil, I figured “emergency situation” and “any oil is better than no oil” (though, granted, I knew better than to put HD30 in there).

On the off chance that my engine actually calls for 10w40, am I seriously endangering the engine by running with 10w30 in there? I know most modern 4-cylinder engines use 10w30 (my previous car was a 1992 Merc Topaz with a 4-banger, and my two previous cars were a 1989 Honda Accord and a 1986 Chevy Cavalier; all three used 10w30), but the Contour appears to have a 6-cylinder engine, and not being a mechanic, I don’t know how much difference that makes. Granted, it may be a 4-cylinder; I haven’t had time to thoroughly investigate.

From the owner’s manual for your car

So it calls for 5W-30, not 10W-40. Unless it is super cold, the difference between 5W and 10W are moot.

What is important, is go change the oil in the engine (yeah I know you just dumped a bunch in, but you have done nothing for the crap that was still in there) don’t forget to put a new filter on. Then you can fill it up with the proper grade of oil.

You added four quarts? You were seriously low on oil – I think the six-cylinder engine takes a bit less than six quarts.

As Rick says, the difference between 10W-30 and 5W-30 is nothing to worry about.

I would worry, though, about how you got to be four quarts low on oil. It’s inconceivable that a modern engine could burn that much oil unless something is very wrong. Or you’ve got a leak.

Thanks - I just tracked down the owner’s manual online and found the same information at the same time you did :slight_smile: But yeah, I think it was 10w30, but it may have been 5w. Unfortunately, I discarded the bottles so that I can’t check.

But you mentioned “super cold”. It’s been below freezing here lately. The engine seems to be running fine with the oil I put in, but I suspect it wouldn’t be a bad idea to take it to my favorite oil-change place and have them do their thing. I’m an apartment-dweller and really don’t have the space to do the whole job myself. Not to mention that I park on the street — a busy main thoroughfare in my town. Not the best place for car maintenance!

I just wonder where the oil is going. I haven’t seen the puddles under this car that I’ve seen with my previous cars, so I suspect the engine just may be burning up the oil somehow.

Oops, I was replying to Rick; Saintly Loser’s post came in while I was typing.

But yeah, as I mentioned, I’m not seeing puddles under the car, so I suspect it’s burning oil. Given that it was a free car, I’m not going to complain, but my plan is to trade it in for something better.

When I said super cold, I meant super cold. -20F or worse kind of cold. At those temps the 10W would be much thicker and make the engine that much harder to start.
The car might be burning it, but who knows how long it has been since the last oil change. Do the oil change, check the oil when you gas up, and track your mileage.

The 5w/10w is merely the viscosity rating at an arbitrary cold temp, and the 30 is the viscosity rating at an arbitrary high temp - I believe it’s 100C.

These aren’t point values, but more like bands- SAE 30 @ 100C means that the oil’s viscosity falls somewhere between 9.3 and 12.5 centistokes (the actual viscosity measurement), so the 5w/10w doesn’t have anything to do with it- it’s entirely possible that the 5w could be 12 cSt, and the 10w could be 9.35 cSt at operating temp (the opposite of what you’d think).

In general, your “W” number can’t really be too low. People think of motor oil as not thinning out as it gets hot, but it should really be thought of in the reverse situation.

If your engine calls for oil betweeen 9.3 and 12.5 centistokes at 100C, then you really want your oil as close to that all the time as you can get.

The problem is that most oils that are that viscosity at temperature thicken up like crazy as they cool off- a straight 30HD oil might be 11.7 cSt at operating temp, but at 40C (a hot day!) it might thicken up to as high as 100 cSt. A 5w/10w-30 might thicken up to 60 cSt, and the 5w will be pumpable and pourable at a lower temp than the 10w.

Clearly the point is to engineer oils that are at the right operating viscosity and that thicken as little as possible, so the lower the first number (the “5w” for example), the better.

When you go next in for fuel, you should do some basic checks. Oil, water, tyre pressures (including the spare) at the very least. Top up the washer bottle with suitable fluid as well if you can. On Fords over here in the UK, all the important bits under the bonnet (hood) are coloured yellow.

Occasional topping up, or even an occasional oil change, with a different viscosity oil isn’t going to ruin the engine. However, consistently using the wrong oil can cause problems.

Field experience has shown that some engines will suffer premature camshaft failure if 10W-30 is used instead of 5W-30. GM changed their recommendations to 5W-30 for some new engine designs in the 80’s after seeing a lot of cams getting wiped out. Ford issued a TSB changing from 10W-30 to 5W-30 which applied retroactively to their engines.

You don’t need to lose sleep over having 10W-30 in it for the time being, but you should make a point of normally using 5W-30.

Hijack: Is there a problem using 20W-50 oil in an old beater engine that’s rated for a lower grade? I ask because years ago, a mechanic suggested that I use that grade to fix a problematic oil leak which would have cost thousands of dollars in repair. It seems to work like a charm, haven’t had any problems in years. However, every time I go to Jiffy Lube and ask for 20W-50, they FREAK OUT and make me promise I won’t sue them for any damage, etc. What’s the expert opinion on this?

The Contour was retroactively specced for 5W20. [pdf]

Well since it is a beater, and you opted for the “heavier” oil instead of the “thousands of dollars fix”, I would not worry about it. You are going to scrap this rig as soon as it has a major breakdown anyway. The worst it will do is to prematurely wear the main and rod bearings. This would be your major breakdown. You will probably not even see that failure if you keep oil in it. Running it one to two quarts low on oil is a major screw-up. That and not the weight of the oil in any car is a condition that WILL ruin your engine bearings.

I worry that the OP did some serious damage to his engine bearings. His engine was at least FOUR quarts low. If it were me, I would pay the extra $$ to the jiffy lube place for an oil analysis. They take some of the old oil and send it to a lab. The lab will send you a report on the oil. It can tell you of an impending engine failure. At about $30.00 it is a cheep diagnostic tool. It will give you some insight as to whether to trade this off quickly or if you can wait awhile. I personally do this every other oil change. This way I can track trends in the engine. I only have one rig that I care this much about though.

IHTH, 48.

Trany fluid too. That can go from “works perfectly fine” to “Oh crap! how the hell did my transmission lock up like that?!” in two seconds flat. There is no gradual demise.

Is it more a problem if oil types, not weights, are mixed? In other words is half the oil being synthetic and half “natural” a bad thing?

(I would assume so more than weight)

No problem there. You can buy it premixed.

Get the ball joints and tie-rod ends checked, it’s easiest to do by having the steering alignment checked, even if the alignment seems fine.

Thanx, 48Willys … I’ll start using 5W30 instead of 10W30.

More, perhaps, than you care to know about engine oil:

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Is that really true? I thought the common wisdom was that running 1-2 quarts low isn’t a problem in itself, but the main risk is that if you lose any more oil, you’re in serious trouble. Or is that advice outdated?

Continued hijack: What about overfilling the oil tank? What kind of problems could that cause?

Oil doesn’t only lubricate. It helps cool the engine, so running it low could contribute to overheating.

Whether one or two quarts low is bad to extremely dangerous depends upon the engine design and its oil capacity at full.

Overfilling could lead to frothing. Ironically, too much oil could lead to oil starvation.

Mixing different types of ATF can be fatal to a trans. Put Dextron in a box that calls for synthetic and the next thing you put in will be a rebuilt trans.
Iffy Lube has found this out the hard way.