1999 Corolla Oil Consumption and Poor MPG?

#1
Hello all,

Thanks for taking the time to read this/help out if possible.

First thing's first, she has 193k on her but still drives like a dream and just always seems to start up without fail. I've done 45k miles on it in the two and half years I've owned it and usually put in a qt every 1k miles, if that, so it seemed to always do this but not this badly, and previously my gas mileage was 29+. I drive delivery for a place in Syracuse and have used my car doing it for a few months now, putting on an average of 75-90 miles per week for work. Within the past couple weeks I've been going through a half quart of oil or so, per 250-300 miles driven and my gas mileage dropped to 16.8 in the city (with some idling), way below what I would expect.

I don't see it burning anything. No blue, white, or black smoke. I watched it while it idled for 30 mins and saw nothing, had a friend drive it around in front of me accelerating and downshifting and didn't see anything. Plus it passed emissions in March just fine. It has some oil on the engine and the intake manifold is blackened with soot, as is the muffler and the back end of the car immediately near it. I've replaced the PCV valve, made sure it wasn't sucking in coolant and tracked my thermostat guage to make sure it wasn't overheating to try and rule out a headgasket. I put cardboard under it for a couple days while I had class but saw no drips of anything. No loss of power from the engine either, she still runs and drives great. The idle is normal too. I read something about the pistons being undersized for the 99 corolla engine which would cause oil consumption later on, could this be it?

I'm a poor college student and just had to come up with $1500 for first/last/security down on a place for the next two semesters while paying my normal rent this month so I'm kinda drained. Which sucks because I would need to get a compression/dripdown test to get a more accurate representation of the problem but can't for like 2-3 weeks, depending on tips.

So what happens if I keep checking the oil and filling it up when it needs it? Bad idea? Anyone have any idea of the culprit from the described symptoms? How long do you think it'll hold up?

Thanks
 
#2
I believe those engine have some sort of plastic for the oil control rings, and they are common to lose oil at those miles.

As long as you keep the oil full, it will be fine, but I'd save up for something else in the meantime.
 
#3
Welcome to the Corolla Forum! :thumbsup::clap::thumbup1::):party::balloon:

At CarComplaints.com, the #1 complaint listed for the Toyota Corolla is oil consumption, however that is only 3 complaints which is not bad at all. http://www.carcomplaints.com/Toyota/Corolla/1999/engine/

What brand and type of oil are you using, i.e. petroleum or synthetic? Have you changed brands in the recent past?

45,000 miles in 2.5 years is very high mileage, 18,000 miles per year. How often are you changing the motor oil?

Stop and go city driving will obliterate a good fuel economy average because when the car is sitting still it is delivering exactly zero miles per gallon. Then having to re-accelerate the car from a dead stop consumes a lot of gas too. Having an engine idle for 30 minutes and not having the car moving will wipe out any kind of decent mpg average.

If the engine has oil on it, then there's an oil leak somewhere. Look into it closely. Gaskets and seals with 193,000 miles on them will tend to wear out, especially with using petroleum oils that allow an engine to run hotter than with synthetic oils and the hot running allows the gaskets and seals to dry out, crack and start to leak oil.

The black soot on the inside of the tailpipe and the area around it indicates the engine is running rich. The black soot is incompletely burned fuel residue. This is not normal. The cause of this will need to be diagnosed. Do you know if the oxygen sensor has ever been replaced? Does the car display any check engine light?

Check the oil level frequently and add as needed. It's less expensive to purchase oil in 4-5 quart jugs than individual quarts.
 
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#4
193,000 miles, car is definitely due for a sensor and most people don't replace them until they throw lights. Should do it every 60,000 miles for optimum fuel economy.
 
#6
Hey all!

Thanks for the replies!

It does not currently have any check engine light problems. It threw a code in February that it was running lean (bank 1) and also showed a catalytic converter code, it would go on and off on its own some times but after I was told by a friend to replace the PCV valve it stopped and stayed off.

In the entire time I've owned the car I have never replaced an O2 sensor, you think that's what's causing the fuel issue?

Also, it's been using 5w30 for the entirety of it's life (or so I was told), no synthetics.

Any idea the cost of replacing one (or both) of the O2 sensors?

Thanks again!
 
#8
Just do the upstream sensor. That is the one that adjusts your air/fuel ratio. The downstream sensor only makes sure the catalytic converter is working and nothing more. I only mess with the downstream sensor when it throws a code, upstream I do every 60,000.
 
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