Unbeknownst to me, since my last oil change, my Mazda 6 decided to drink 3 courts of oil…leaving my engine severely lacking the all important lubricant. As one might expect, issues arose and now I am faced with the deadly rod knock. 
I am trying to weigh the options of buying and installing a rebuilt engine or junking the car all together and getting a different vehicle. The car is a 2007 Mazda 6 i Sport 2.3L 4Cyl with 97,000 miles. The blue book is only around 4200.00 for the car. My first estimate for a rebuilt installed was between 4200.00-4500.00 in total. Do I keep looking for lower repair estimates? I just want to make the smartest decision under the circumstances. Any guidance is greatly appreciated. On a side note, my Dad hates foreign cars and votes I trash it and get an American made vehicle. 
“my Dad hates foreign cars and votes I trash it and get an American made vehicle.”
It’s sad that your Dad is so badly misinformed, as your car–like the other Mazda 6 models sold in The US–was manufactured in Flat Rock, Michigan. Would he prefer that you buy a GM, Ford, or Chrysler product, many of which are manufactured in Mexico, or Canada, or Korea?
Hmmmm…
But, to return to the topic at hand, I would base the decision of whether or not to overhaul the engine on the condition of the rest of the car.
Is it rust-free, or is rust starting to become evident? Once rust damage starts, it can take its toll quickly, because as the song tells us, Rust never sleeps.
If it has an automatic transmission, have you had the trans fluid changed at least 3 times so far? If the answer is “no”, then you are likely facing a trans rebuild in the near future, to the tune of…probably…~$2k. (If this is a manual trans car, then this is one issue that you don’t have to worry about!)
So, if your car doesn’t have any other looming repair issues that were deferred, if it is rust-free, and if you have serviced the transmission as described above, it would probably be much more fiscally responsible to have it repaired and then continue to drive it for a few more years.
However, the main lesson that you should carry with you as a result of this situation is that cars–especially those that are no longer new–need to have their oil and other fluids checked and topped-off regularly. Ignoring things like checking fluid levels between oil changes is one of the leading causes of engine and transmission destruction.
So, whether you decide to keep and repair this car, or whether you decide to ditch it and buy another, PLEASE do an under-hood check every 3 or 4 weeks. If you aren’t comfortable doing this yourself, perhaps you can enlist the help of your father or a friend.
If you didn’t have any excessive oil consumption issues before this then I would have to wonder if the proper amount of oil was put back into the engine after the oil change.
Like @VDCdriver stated, I also agree that if the rest of the car has no major issues and you want to keep it for at least several more years then I think you should have the engine repaired. The quote you got really is pretty much in line for that kind of work. If you do have the work done make sure you get at least a six month warranty on the service work done.
I recently saw a news report on the top 10 auto manufacturers for reliability. Buick was the only American name on the list.
A $4,000 repair for a vehicle that will only be worth $4,500 after repair is a awful and financially bad choice.
So running your car is worth $4,200. That means you could buy one that is similar for that amount. Your car as it sits today is likely worth about $500-$1500 assuming the body and interior are in great condition. You would be better off to buy a different car and sell the one that you have. Someone will buy your car with known engine problems and they will DIY engine repair and have a decent car for a good price and a weekend of their labor.
On the other hand, if the car is otherwise in good shape, where else are you gonna get a good used car of known history with a newly rebuilt engine for $4,000???
If the car is otherwise in good shape, I’d go for the engine. A car’s value in reality can be much greater to the owner than its market value, simply because it might cost a lot more to get a comparable vehicle and other used cars have unknown risks.
Buying a different car gets you into something you have no history on. Fixing what you have gets you a rebuilt engine that should have a warranty with it also. She also has fairly low mileage on her car for the age of it. You can’t usually get something like that with a $4k used car.
I agree with TSM. Buying a used car, specially one almost 10 years old, is a big gamble.
Me, I’d get a new car.
I don’t know your financial situation or whether you use the car for long trips as well as local driving. The condition of the body and chassis is very important. Spending money on a rusted vehicle doesn’t make sense.
Don’t go for the lowest estimate. If you do fix the car, go to a reputable shop and have the rebuilt engine installed. Our son has a Chevrolet S-10 pickup. The body is in great shape, but it blew a head gasket last summer. He went for the lowest price. The head gasket was replaced, but it blew again. He decided that all he needed for a second vehicle was his motor scooter. The truck sat for several months while he debates what to do. I finally convinced him to have it towed to a reputable shop and let them sort it out. When they pulled the head, they found the first repair wasn’t done correctly. He now has a truck that is running and the bill from the reputable shop was less than the first repair. The moral is that if you get the Mazda repaired, have it done by a shop that will do if right. Don’t go for a sloppy patch. In my son’s case, the motor scooter won’t run. It also needs tires. He is trying to figure out if it is worth the repair.
Thanks for all the really great feedback. I do like the Mazda, overall, and the body is in good condition, no major body issues or rust. I am really not terribly excited about shopping around for a used vehicle for exactly the reasons people shared. VDCdriver, you are correct…lesson learned with checking your vehicles fluids regularity, and that will happen from now on. Thanks again everyone!
@KKlungseth
Do I keep looking for lower repair estimates?
Definitely!
Some auto salvage yards have sales lots attached to them. Often, they’ll get a car with a blown engine or transmission that somebody has scrapped, that is in otherwise nice condition. They use the engine or transmission from a wrecked vehicle that was scrapped because the body was damaged. Many have lots of experience locating and installing decent engines.
That engine or transmission goes into the car that had a blown one and is put on the sales lot for sale. I have 3 such lots near me in a very rural area. Local folks buy these cars and they serve them well.
I’m not saying to go buy one of these cars. What I am going to say is to go and see if they’ll install a good engine in your car. Many of these shops would be very inexpensive compared with others. I’d bet they will give some kind of warranty, too.
CSA
“A $4,000 repair for a vehicle that will only be worth $4,500 after repair is a awful and financially bad choice.”
Disagree. Its not that simple.
First is an evaluation of the present vehicle. As mentioned above, body rust free, no dents, paint in good shape? Interior clean and looking good, no tears, worn carpets?
Now for the mechanical stuff. Brakes, when were they last done or when will they be due. Transmission fluid (ATF), is it still bright red? Tires, how much tread left?
The evaluation is needed to see just how much you might need to spend on other things in the near future. If the ATF is black, the brakes about due and the tires are bald, you will need to dump quite a bit of money into this after replacing the engine.
Now you need to evaluate the ROI (return on investment) that you expect to get if you do put money into this. This car probably cost around $20k new. So far the amortized purchase price is about $0.20/mile. A new similar car would run about $25k so the first 100k miles would amortize at around $0.25/mile.
This is not total owner cost (TOC) which would be 2 to 3 times that. I’m not going to include TOC because first of all, all the expenses other than purchase price or repair cost will be about the same, so including the TOC only makes it unnecessarily complicated.
If the oil level hadn’t dropped and you otherwise kept good care (maintenance) on the vehicle, you could expect it to last 200k+ miles. That would have put your amortized cost per mile of the purchase price down to about $0.10/mile.
A good remanufactured engine that is taken car of can last another 100k to 150k miles. Investing another $5k into this car and adding that to the purchase price brings the amortized purchase cost to around $0.125/mile (@200k) or less. At 250k, you would be back down to your $0.10/mile.
At your present $0.20/mile if you dump the vehicle, a $4500 investment would pay back in 22,500 miles. Every mile after that starts to lower the amortized purchase and repair cost.
I recommend a remanufactured engine over a junk yard (aka used) engine because you get the best ROI with that. I think it is cheaper to keep her. But do learn to check the oil and do it regularly and especially do it before you leave the oil change place and again the next morning before you start up the engine.
BTW, has anyone checked to see if the drain plug or oil filter was left loose?
Just curious, but did the engine in your car show any signs of oil consumption or knocking before this last oil change?
Who did this oil change and how long afterwards before you noticed the problems
“did the engine in your car show any signs of oil consumption…before this last oil change?”
That is definitely a reasonable question, but in light of the OP’s admission that checking oil was not one of her…priorities…I’m not sure if she would have been aware of oil consumption prior to the current situation.
@KKlungseth
Approximately how Many Miles Was It, Between That Last Oil Change And When The Engine Was Found To Be 3 Quarts Low?
CSA
My daughter had an almost identical experience with a Toyota RAV4.
She opted to get a Jasper rebuilt put in because her car was in otherwise excellent condition. The repair bill came to more than the estimate ( Well, you wouldn’t want us to re-use your old belts, hoses and fluids , would you?)
The first engine started leaking oil from the head casting, the second suffered intermittent rough running and vibration despite numerous attempts of the shop to fix it, it always returned.
After 3 years of inconvenience and frustration, she traded it in and deeply regrets replacing the engine to start with.
depends on the condition of the car (mechanically and body-wise). Also… Do you enjoy the car, do you like driving it? That’s what I’d ask myself.
@tmanp
KKlungseth, said, "Thanks for all the really great feedback. I do like the Mazda, overall, and the body is in good condition, no major body issues or rust."
CSA
My first impression based on your post is you’ll be better off buying another vehicle. Replacement engines, often b/c of the computer systems involved in cars these days, often come with a host of installation and compatibility problems that require the owner to return the car to the shop multiple times before they all get taken care of. And in some instances reported here they never do get resolved completely.
Now if you are the scientific type and would enjoy a little challenge in logic and physics, it might be some fun. But if what you want is a reliable ride, sell this one and buy another car. Someone who’s interested in a challenge will be happy to give it a go on your car. But let them do it at their time and expense, not yours.
Replacement engines, often b/c of the computer systems involved in cars these days, often come with a host of installation and compatibility problems that require the owner to return the car to the shop multiple times before they all get taken care of.
I have never had a problem like that after replacing an engine, I think that is just an excuse for poor workmanship.
I think that is more of an issue with used engines as there is a tendency to keep all the sensors on the used engine and some of them may not be compatible with the PCM and or BCM. A reman engine will be delivered without any sensors, so the mechanic has to transfer all the sensors from the old engine to the new one and that should eliminate the problem.