You are the victim of misinformation and unfortunately very poor communication which we are known for. I suspect you are not the victim of fraud or incompetence.
It is true a lot of engines use oil between oil changes and you aren't going to stop that. In fact, to address the numerous complaints about that way back to the late '80s, the markings on oil dip sticks no longer show "add" and "full". They are labeled "min" and "max" now. The specified amount to add during an oil change doesn't quite bring the level to the "max" line, and as long as the level is still above the "min" mark, there's no need to add any and no cause for concern. Many engines go through considerably more than a quart in a thousand miles so you need to check the level at every gas fill up.
The next issue is oil is to an engine like blood is to your body. You absolutely can't be without it for even a few seconds without starting some damage. With only one or two quarts in an engine, there are going to be times, like going up or down a steep hill, or going fast around a corner, when oil starvation occurs. If you were two or three quarts low right after your last oil change, there is no way you would have made it 1,000 miles. That tells me the last mechanic didn't do anything wrong when he changed your oil. They didn't do a good job of explaining that to you or they didn't bother to try because they already felt they were on the defensive and anything they said would just add fuel to the fire. When we're in an argument, it's hard to try to win with reason and logic, especially when we're working with the typical car owner who doesn't understand how engines work and what can go wrong with them.
Just like doctors, accountants, carpenters, and butchers, mechanics have their own language and they communicate real well with other mechanics, but not with customers. That has a real lot to do with the undeserved bad reputation we have just for being a mechanic.
As for the knocking, once that starts, you're done. Just as with a heart attack, there is nothing you're going to do now without the proper repair. The crankshaft bearings and connecting rod bearings are thin curved strips of metal that have a tiny space, (clearance) of around.005". That clearance between the crankshaft and the bearings is filled with oil under pressure to isolate the moving parts from each other. The knocking you can hear is the result of WAY too much clearance; typically 1/8" or more. That increased clearance is the result of lack of pressurized oil and the metal parts rubbing and grinding against each other. Once that starts, the extremely soft metal bearings get chewed away very quickly. Those parts originally had a mirror finish on them, and once a rough patch appears, it tears the bearings up in a matter of a few seconds. I've had two vehicles that happened to but in my case I had free labor from my students. Parts cost around $400.00 and engine machine shop services cost around another $200.00, so it paid to rebuild those engines. When you have to pay for many hours to remove and replace the engine, and the typical shop has to take the engine to a specialty shop to be rebuilt, most mechanics who have your wallet in mind will recommend a used engine from a salvage yard as a less-expensive alternative.
There is no value in trying to do a quickie repair by replacing just the crankshaft and bearings. In 90 percent of those attempts there are already metal chunks floating around in the oil, and those are going to cause continuing damage to a repaired engine. Every time I've watched an expert try to save his own engine that way, it ended in disaster. No professional, armed with that knowledge, is going to risk the same thing for you. The only way to be sure your engine can be rebuilt and be just as reliable as it originally was is to have it totally disassembled so all the oil passages can be thoroughly cleaned. When it comes to engines, you have to do it right the first time or you'll have to do it a second time. You won't be happy if you have to do it a second time and your mechanic knows that.
As a point of interest, in my book, yours is not "an older car". To me it is very new, and it's the newer ones that use more oil between oil changes. You need to keep an eye on the level much more than with the stuff I drive. Ford was one of the first to say oil usage was "normal". They started using "low tension" piston rings to reduce internal friction and supposedly improve fuel mileage by a few thimblefuls per tank, but severe oil consumption was the unintended result. GM added to the problem by using very light weight oil like 10W-20 or even 5W-20 compared to the much thicker 10W-40 we used to use. Thin oil will be okay as long as there are no other underlying problems. It sneaks past the piston rings rather easily so the level is almost guaranteed to go down as you drive.
I suspect the responsibility falls on you for the low oil level, but at some point someone should have made you aware that checking the level often is much more important than it was in the past. That again has to do with poor communication.
Be aware too that you won't always see blue smoke from the exhaust when the engine is burning oil. When you do see that smoke, the oil is being burned at a very much faster rate. Also, while I understand you don't see any evidence of a leak, it is not uncommon for oil to drip into a frame cross member or puddle somewhere else, then blow off at highway speed. Typically you'll see the underside wet with oil toward the rear of the vehicle, but not always. To find that you really need to have the vehicle on a hoist so you can do a complete inspection. Simply peeking underneath or checking for spots on the ground isn't sufficient.
Sunday, March 27th, 2016 AT 9:45 PM