Only for a short time
Very well said G-J.
Also, if your car is consuming oil the most common reason is the oil rings on the pistons are worn or the springs under the rings are clogged, broken or just fatigued.
Fatigued can happen as a result of high temp and that is what happens when running low on oil also.
There can be some relief from excess oil consumption by using an additive but also consumption can be slowed by using a higher viscosity oil like a 40 weight in place of a 30 weight when the engine is high mileage.
If you have intentions of rebuilding the engine, do so sooner rather than later.
Ditto, it’s an emergency crisis indicator. This is a bit like letting smoke be your indicator that you should disengage the parking brake.
It’s nice to have because if it comes on you may be able to pull over immediately, shut down, add oil, and not have any permanent damage. But I sure wouldn’t drive to the nearest place that sells oil, I’d walk there.
Car manufacturers build a wide margin of safety into their oil life model (or their change interval spec in the owner’s manual). If it says you can drive X miles between oil changes, you could *probably * double that before the additives/detergents in the oil were truly and completely used up. This is not to say that you should endeavor to find that limit, but there’s a lot of room for being casual about it. If the oil life monitor says “0% left” after 7500 miles, you could certainly go to 9000 (i.e. another 1500 miles) if it’s not convenient for you to change your oil any time soon.
Not me, but friends of mine have confirmed this by having their used motor oil lab-tested.
OTOH, if you buy a 15-year-old Nissan, Toyota, or Honda for $900 and drive it until it dies, the odds are that “low oil” won’t be what kills it. There’s a huge number of things that can go wrong and eventually one of them will. If you decided to wait until the oil light comes on before adding oil, you’re shortening the life of the car, but probably not by much. I mean, let’s imagine 1,000 such old Japanese cars purchased for $900 each. In half of them, we’ll get the oil changed every 3,000 miles and check the oil every day and top it up to full all the time. In the other half, we just wait for the oil light to come on then add a quart, and only change the oil twice a year. Both groups are going to have things go wrong, broken axles, burned out clutches, leaking radiators, malfunctioning ECUs, et cetera. Suppose two years later, we check back in with both groups and find that 41% of the well-oiled group is still on the road but only 37% of the idiot light groups is still on the road. Okay then, we figured out that there’s a 4% chance that your bad strategy caused a premature death of your $900 car, meaning the strategy cost you .04x900= $36. The question is, did you save more than $36 worth of time and oil changes? Is it worth $36 to you to not have to get your hands dirty twice a week checking the dipstick?
Yeah, I just made up those numbers, but the point is that just because something has a down side doesn’t mean that it must be the wrong choice.
I had a co-worker who would add oil when the light came on. Once he put in 3 quarts in an engine that only took 4.5 quarts! Eventually the engine seized and he just couldn’t believe that adding a few quarts of oil wouldn’t fix it.
On the other hand, I once owned a 1972 Toyota Corolla that would have the oil light come on at idle. I checked the oil pressure with a pressure gauge and it was just fine. I went through 3 oil pressure switches before the problem went away.
Teach her to add “Check my oil level” to her list of Saturday choirs. I suspect she’s not real religious about changing the oil at 4 to 5 thousand mile intervals either. Changing oil is the single most important thing you can do to extend the longevity of any engine.
Perhaps it’s better if you did a monthly inspection of her car, fluids, oil, tires and tire wear, wiper blades, etc. By doing this, you’ll save her a lot of inconvenience and money in the long run.
Maybe, but if you bring your vehicle in for a warrantee repair they’ll use any excuse necessary to avoid paying for it, and running 1,500 miles beyond the stated oil change interval is one they’ll grab in a hurry. If you’re already beyond the warrantee period you could go for it. I know I’ll stretch the service intervals once I get past 100,000 miles.
I had an old Volkswagen beetle years ago - the giveaway that oil was needed was when the oil light came on during sharp turns.
We used to have an Audi A4. I drove it for about 100,000km and then it died. Basically, there was a flaw that the oil could overheat (we had areas of the country where 100mph was not difficult to do for several hours). The dealer would only say “we put in the recommended oil at all servicing intervals” but the recommended oil was not synthetic oil until the third year we had the car. Overheating oil would gum up - in this case, all the oil channels. As a result, although the oil pressure sensor saw sufficient pressure, downstream from that was constricted and the car was not getting enough oil. When the engine was finally flushed before an oil change (first time not at the dealer), the oil light would come on every time the revs dropped to near idle. A common problem with the turbo Audis was hot oil gumming up the oil intake so the engine starved.
General thought was likely the bearing race for the crankshaft bearings had worn badly. Options were - replace the crankshaft bearings, replace with new engine, or replace with used engine. The first choice was a gamble - if other parts were also badly warn, we’d spend a fortune to get a still failing car. Audi engines were tightly tied to their computer, so replacement was a gamble too - plus with a used engine, who knows how it had been treated (and why it was used).
In the end we’d spend almost what the car was worth (with a good engine) to end up with a car likely still badly flawed. In the end we traded the carcass to the Audi dealer for a used car, not an Audi. (At least they could replace the engine in their maintenance department’s spare time for cheap).
So there’s an example. Oil not only lubricates, to some extent it cools. Using a quart and a half to do the job of 4 to 6 will result in the engine overheating, wearing faster, burning the oil so it gums up the oil channels, and generally causing problems. Your engine may not seize right away, but it will wear much faster, resulting in even faster oil consumption.
Actually, she is pretty good at changing the oil every 5000 miles. Awhile back I had her change the oil at around an even number of miles (75000). When it got to 80000, she changed the oil, 85000, etc, etc.
As far as a monthly inspection goes, she is my sister in law, not my wife. There are no “benefits” to being that helpful.
so it’s losing enough oil in 5,000 miles where the oil pump is sucking air? That engine is trashed, and if she wants to continue using that car she will have to get her hands dirty.
honestly, if the automobile was invented today, none of us would be allowed to own one.
Most choirs sing on Sundays. And “Check my oil level” must be from a different hymnal than the one I use.
Edit: Wrong thread.
If the engine is pretty close to trash, and the car presumably is so old or used that there’s no point in doing serious engine work on it… then all she needs to do is keep adding oil until it dies. Hopefully it dies somewhere convenient, like a “no parking” zone and the city will dispose of it for her 
So it’s a terminal patient already, she might as well drive it until it dies. Just keep topping it up. An interesting exercise - fill to the top line on dipstick, then see how much difference there is to bottom line on dipstick. Learn to add a quart (or half quart from a re-sealable bottle) every so often, and she can drive it until it dies. A few quarts of oil, then a cab ride when it dies, is cheaper than one month of new car payment; so any time she can get out of it is bonus.
But yes, oil at least to the bottom level of the dipstick lines is always better than even less.
is it possible she just never learned these things? I mean, I learned from my dad how to take care of my car. I have been grateful for these lessons all my life - no matter what, at least I have some idea of what to do for my car, even if I can’t physically open the lugnuts or whatever.
Although I agree it’s irresponsible not to read the owner’s manual if you don’t know these things. Hell, I still use the owner’s manual for some things.
Exercise for what? There’s nothing to learn here – from the top (“full”) line to the bottom (“low”) line on every engine oil dipstick I’ve ever seen the difference is one quart.
Check often enough, add one quart when the level reaches the “low” line. Simple as that.
I’ve assumed that, but haven’t have enough experience with different vehicles or oil shortages to verify it. Thanks for the info.
On my pickup (which is admittedly diesel), the difference is two quarts, and one of my relatives had an old Suburban where the difference was something like 1.5 qts.
Yes, on passenger cars, one quart is the usual standard.
Some cars have a traditional oil light, and an indicator for “low oil”. My Buick LeSabre has both. I’ve never had the pressure light come on, but I did have the “low oil” indicator come on once.
My BMW oil light actually has three modes: yellow after turning car off means it’s a bit (~1 qt) low, so add when convenient; yellow when driving means it’s very low and you should add oil immediately, though it’s still not at a critical level; red means the oil pressure is below the minimum. Never seen it red.