Car eats oil - oil change interval?

2001 Corolla CE; 140,000 miles; city driving, 12-15k/year:

Car eats a quart of oil every 300-400 miles (ran it low on oil a few
years ago.) I’ve just been adding a quart of 10W30 (hi-milage) every
week or so. (I don’t want to spend the big $$ to get it fixed, so I’ll
just keep driving it for a while longer, then sell it what whatever
someone is willing to pay.)

Now, giving the oil consumption rate, I’ve been adding several quarts
of oil between oil changes, and so, if you think about it, the engine
always has pretty fresh oil in it So, how often should I be taking
it in for an oil (and filter) change? Use a less frequent interval?
Or perhaps the ‘regular’ interval because the filter is getting extra
dirty.

TIA
Bubba

 

2001 Corolla CE; 140,000 miles; city driving, 12-15k/year:

Car eats a quart of oil every 300-400 miles (ran it low on oil a few
years ago.) I’ve just been adding a quart of 10W30 (hi-milage) every
week or so. (I don’t want to spend the big $$ to get it fixed, so I’ll
just keep driving it for a while longer, then sell it what whatever
someone is willing to pay.)

Now, giving the oil consumption rate, I’ve been adding several quarts
of oil between oil changes, and so, if you think about it, the engine
always has pretty fresh oil in it So, how often should I be taking
it in for an oil (and filter) change? Use a less frequent interval?
Or perhaps the ‘regular’ interval because the filter is getting extra
dirty.

TIA
Bubba

Sounds like your oil is being changed continuously so no need for an "oil
change" though I would change the filter at whatever the recommended
interval is for the car event though the oil going through it is cleaner
than in a non-burner.

 

so is the car eating the good oil or the bad oil equal quantities of
each? Its probably eating the good oil. I would say change the oil and
filter every 2,000 miles or so.

 

The oil is mixing together--- and why would you recommend changing it so
frequently? It's barely dirty at 2000...

 

You need to find where the oil is going. Leaking it is one thing,
burning it is another.

 

No oil leaks. My mechanic says the oil is burned in the catalytic
converter.

 

You should anticipate having fun at your next state inspection

 

It passed emissions test a year ago, and it had been eating oil for
two years.
Next emissions test is in 1 year

 

Then the engine has internal issues of one degree or another. Unless you
track down the specific causes of the oil getting/remaining in the
combustion chamber you may not want to count on it as being a 'self
changing' system as oil is added to make up the difference.

 

Yup.
Also, I'd try something thicker than 10W30; 10W40 or 15W50; to see if
that slows the oil burning.

No worries about that now. Given a choice you want to buy oil filters
with the greatest capacity. But it really doesn't matter. Your engine
won't notice.

 

Intuition says that since you add so much oil, the oil is always fresh.

The truth is that an engine so unbelievably worn out (especially in this
day and age with only 140k miles) as to burn a quart in 300-400 miles is
also blowing HUGE amounts of combustion byproducts into the oil, so that
the oil is contaminated at a rate many times faster than a healthy engine.

 

The truth is that an engine so unbelievably worn out (especially in this

I agree, and I'm also guessing that the car has reduced power and
mileage and really low compression. I'd do a compression test to see
if maybe there is a problem with one cylinder and maybe you have a bad
gasket, or something. But that's only if you are lucky. I'm guessing
that it needs to be rebuilt, or a ring job at the very least.

 

He said that the cause was he ran it low on oil several years ago. The damage
that is causing high oil consumption is probably to bearings, crank, rings,
and cylinder walls. Given the other information he gave, it makes no sense to
rebuild ( there is no way rebuilding will increase the value of the car by more
than it costs) and there is no reason to believe the engine won't last a long
time in it's present condition if it is driven sensibly and the oil is changed
frequently.
Since it passes emissions tests, it probably gets good gas mileage and if he
isn't interested in winning any races the performance is probably more than he
needs. I would do like someone else suggested-> Buy a case of oil (12 in a box)
and filter, then change the oil and filter and add oil as needed. When the case
is used up do it all over again. It would be a good idea to use at least 10-40
in the summer and go back to 10-30 for the winter.

-jim

 

there's no evidence a heavier grade of oil gets burnt slower. in fact,
the flash point of heavier grades is often lower.

 

That would be an interesting discussion , but I doubt that it matters much. If
he ran the engine out of oil (or low enough that the oil pump was sucking air
and the engine started to clatter) then he may have scored the crankshaft and
bearings. Cylinder walls may also be scored. The oil pump could have also been
damaged. In hot weather if the oil isn't thick enough the oil pressure could
drop to the point where more damage will occur. Also a heavier oil may reduce
oil consumption.

-jim

 

Try an oil change using Delo 15w40.
I have had tremendous luck in burners with this stuff.
HTH
Ben

 

eh?

 

Eats oil? Is it chewey?

You should change it more often, while its still thin enough to drink.

 

I don't see why the flash point would matter since any oil that finds
it's way into the combustion chamber will be burned. I had always
assumed that the conventional wisdom was that viscosity oil would
resist being sucked into the chamber as readily which would reduce oil
consumption.

 

Heavier oil does get consumed more slowly by worn engines, within
limits. The upper number isn't as important as the cold viscosity,
though; 15W-whatever will work better than 10W-40. For the same reason,
there is little advantage in going from 10W-40 to 10W-30 for Winter,
because it's the starting viscosity that matters most in cold weather.