My mechanic is confused

toyota
corolla

#1

My mechanic cannot figure out what’s wrong with my car, so I’m hoping this community can help me. My car is a manual trans 1996 Toyota Corolla with almost 154K miles. I had the oil changed two weeks ago (about 1000 miles with my commute), and at that time, I let my mechanic know that it’s been losing oil and to please check it over. At that time, he changed the oil, cleaned the engine, and added a dye to the oil to show up any leaks.

I took it in this past Thursday for him to locate the leaking, and the mechanic let me know that 1) It came in mostly dry (no oil), 2) there was no visible leaking except for a seepage around the oil pan, which he says could not account for the loss of 4 quarts of oil in two weeks, and 3) it’s not burning it out in the exhaust system.

A bit of the history of the car. I got it when it was at 59K, used, and there were a number of things wrong with it that I didn’t discover until later, such as that no maintenance had been done to it at all in the 60K someone else had owned it. It came to me needing a timing belt, brakes, and an engine and radiator flush (the radiator fluid was brown instead of green).

At one point at around 70K, as a stupid teenager, I did let it run dry. The oil light came on, I panicked, shut it off, dumped in two quarts (which brought it to full on the dipstick, which I thought was weird), and took it straight for an oil change, where they told me it was dry, which was odd, because I’d just put 2 quarts in it.

After that, there were no issues until it hit about 120K. At that point, I started smelling burning oil and there was smoke coming from under my hood, so I towed it to my mechanic at the time. He replaced the valve cover gasket, the rear main seal, and the head gasket (with engine block machining and all). That more or less cleared the problem up, but then I took it across the country on a 3K road trip, and it ended up accidentally running dry again. Oil light came on, I shut it off, dumped in oil, took it for a lube job.

Since that time, it’s been occasionally throwing me an oil light when I go downhill (I figure that this is because it’s low but not out, and the change in pitch reduces the pressure?). Each time it does this, I’ve shut it off, coasted to a stop, dumped in 2 quarts (which brings it to full on the stick), and gone on, berating myself. These times have become more frequent, however, even though I now check the oil regularly.

So before I endure the deserved lectures about being dumb, yes, I blame myself, but regardless of my lazy maintenance, it’s becoming ridiculous. My car is now finding a way to lose a gallon of oil over the course of 1000 miles, with no discernible leak or consumption.

Also, if someone can answer why my oil light comes on when it’s only 2 quarts down on the stick sometimes, and then sometimes goes almost dry without throwing the oil light? That confuses me too.

Thank you in advance for any help or wisdom anyone can offer. My mechanic is truly stumped. I just got it back with the oil topped up, more dye in the engine, and instead of going for 2 weeks, I’m going for 1 week to see if maybe he can catch it in the act of learning this magic trick of vanishing oil.


#2

It’s burning it. The earlier 1ZZFE engines had a design flaw in that some of the oil passages in the pistons were not large enough. They would sludge up with oil and the oil control rings could not do their job. Toyota quietly improved the design around 2003. The fix is to either rebuild your engine with the improved pistons or to replace it with a rebuilt engine that has the improved pistons.


#3

There’s no mystery. The oil is being burned, as mark9207 said. You’d be surprised at how much oil an engine can burn without any appearance of smoke in the exhaust.


#4

Either your engine is leaking oil, it’s burning/otherwise consuming it internally, or the oil fairy is visiting your car and making withdrawals. The first problem has been addressed and found to be no significant issue. The third is highly unlikely. This leaves the second scenario.

Simply replacing the head gaskets will only cure external oil leaks. A complete cylinder head rebuild or replacement will cure oil consumption if it’s related to valve train issues. Wear or damage to the lower end (block and pistons) will only be addressed during complete engine disassembly.

As has been noted above, oil rings can be the cause of excessive oil consumption. Habitually running an engine low on oil can cause piston ring failure in the best of engines, and yours had a marginal ring design to begin with. Your answer likely lies in major engine rebuild or checking and adding oil at every gas fill-up.

There is a small possibility that your problem is caused by a faulty PCV/breather system. Have your mechanic look into that before condemning the engine.


#5

If you have the 1.6 liter engine, you have the 4A-FE

If you have the 18.8 liter engine, you have the 7A-FE

I’m not entirely sure about the 4A-FE, but the 7A-FE is well known for using A LOT of oil. The problem is on the bottom end. To be specific, the coked up and stuck oil control rings are the problem.

You can fix the external oil leaks, replace the pcv valve, etc., but nothing short of major engine work is going to fix that bottom end problem

How do I know this?

Because I wrench for a living, and me and my family have owned Toyotas for well over 30 years

Plus, I regularly read the professional trade magazines

I wish I could say that lax maintenance is the cause, but such is not the case

The real problem, in my opinion, is a weak design

Toyota never officially fessed up to the problem, not that I’m aware of, anyways, and I’ve been on there technical website regularly, over the years


#6

@db4690‌

“If you have the 18.8 liter engine”

Wow, that’s like 1150 cubic inches of engine. Must be for an aircraft application.


#7

@asemaster‌

Funny! I was going to comment about that, but not having as much automotive knowledge as either of you, I decided to sit here quietly.


#8

18.8 liter engine

That would surely be one of the bigger 4 bangers out there

LOL


#9

Why confusion or magic issues? This is Mechanics 101. If it’s not leaking then it’s burning it either past the valve seals or the piston rings. While it could be both, it’s more than likely the latter.

You describe the engine as having been run dry of oil. This only exacerbates a piston ring and/or cylinder wall problem.
Odds are if a dry and wet compression test is run the answer will be pretty obvious.

You also state you bought the car used with 60k miles on it and no maintenance having been done on it. The current oil consumption problem was created by the person, or persons, who owned the car before you did.


#10

Many of these Toyotas with the stuck oil control rings were very well maintained . . .

I say weak design

But poor maintenance just compounds the problem


#11

No matter, the car was damaged goods when purchased and allowing it to run dry 10k miles later certainly didn’t help it any. Even running an engine chronically low on oil is tough on rings; and everything else.

It’s time to consider car shopping or springing for another engine as a gallon per 1000 miles is near the end of the road.


#12

I have nothing to add or change about the fact that the oil is being burned, and with the whole history of the engine, this is no surprise.

But, on the question of the oil light on your dashboard, that light doesn’t have anything to do with the quantity of oil in the car. It is triggered by oil pressure. I’m sure that if you had the pressure checked with a gauge it would be found marginal to too low. The oil pressure problems most likely come from the same things as the oil burning. The engine is worn out/damaged.


#13

Well… damn. I can’t say as I’m surprised, but I was hoping for better news. I’ll let my mechanic know. How much longer am I likely to be able to keep it going if I refill it regularly? I’m not in a place financially where I can buy a car right now… but while we’re all here, what can you all recommend in a nice Subaru Crosstrek or Forester? Because it looks like I’ll be car shopping within the year.


#14

Personally, I think this situation is the relatively rare good candidate for trying out a “mechanic in a bottle” or two. It’s not normally wise, but you have a car that probably isn’t worth fixing (though you might ask your mechanic to price out a salvage yard engine), and you want to just see how long you can limp it along. There are several products around that claim to help with compression and oil consumption problems. You might ask at your shop to see if they have any to recommend, and give it a whirl. Note that even if it helps, this kind of thing is just a “limp along” method - not in any way a real “fix.”


#15

Since the weather is turning warmer I’d also suggest switching to a slightly higher viscosity oil, like 10W-30, if you’re using a lighter weight oil now. A slightly heavier oil won’t be consumed as rapidly. It won’t be a fix, but could lower the rate of consumption somewhat.

The engine will continue to burn more oil amd lose power slowly, but if you keep the oil topped up you might be able to get another year out of it depending on how much driving you do.


#16

This engine has to burn oil, it is not possible for it not to burn oil. Switch oil to 15w40 and see if it is manageable.


#17

Check the oil every 200 miles or every other day. 10W-40 or 15W-40 may slow down the consumption a bit. Drive conservatively–fast acceleration and deceleration increases oil consumption. You have an 18 year old car with 159,000 miles. If you are careful you may get another year. I did this with my first car–a 1947 Pontiac. It used about a quart every 250 miles. I didn’t push it hard and drove it another year. After I sold it, it was still being used three years later.