where is the oil going? + other silly questions

[dosmastr]

Hi again,

This is more a curiosity than a real problem.

The same 94 prizm (with a 96 corolla motor in it) that I’m doing cooling system work to has a peculiar issue.

Its somehow getting rid of oil without a trace. After about 1500 miles its on the low line on the dipstick. I know some oil usage isn’t uncommon or bad but I had a like model that didn’t use or leak a drop (bad first car too… got me out of the habit of checking the oil.)

Its always in the same parking spot overnight, there is never a slick under the car. (the underside is wet but its cause the power steering pump leaks, he is my next project)
The haynes manual says the compression of the cylinders should be 190psi. and yep all 4 are 190 so its not blow by (right..?)
Its not really a problem, I just watch the oil and fill it every 1000miles, just curious what it could be if it doesn’t appear to be burning it or leaking it. A leak I can’t find that evaporates rather than drips?

A little additional info is that when its oil change time (3000ish) I do smell gas in the oil… probably an injector issue right? (if he is the problem, that may need to be done before the pump… i like my rings intact and functional.)
Anecdotally, this car failed emissions inspection for hydrocarbons at low idle, had an oil change, and passed inspection without anything else being done (of course it failed after I had replaced the plugs, wires, distrib cap, rotor, oxygen sensor, PCV valve and cat…so it should;ve passed the first time!)

The answer someone gave me on that was that the equipment they use to test can vary from day to day and the oil change didn’t really do anything. Thoughts?

Topic

[Its me]

Toyotas of this era were known for their oil burning…. On 1.8’s the piston ring lubrication holes were too small and get clogged. The 1.6 was known for being a hot running engine which caused the oil to breakdown too fast and caused the rings to stick… Also bad valve seals caused oil burning… 10-30 oil may help and it may not…

-Karl

[dosmastr]

Hi Karl,

Thanks for the heads up. I did not know that about either of those motors.
Mine being a 1.6L ….. I’ve seen a couple crack-pot looking sites that say running the engine hotter than recommended (using a higher heat thermostat) somehow improves fuel economy (if it were that simple, and had no trade-offs I’m sure the OEM’s would do it) Perhaps there is a small bit of truth to it and thats why toyota had them run hotter?

I guess I was looking at it overly simplistically, thinking if it was burning oil it would have to be oil slipping past the rings.

I did try lucas oil stabilizer, no discernible effect. (I did have a subaru once that sounded awful and lucas did make a huge difference… so far he is the only car of mine to experience any different though)

Maybe the one I had (back in 2004 to 2007, 96K to 166K) had been rebuilt or was a gem or something, he never used a drop! (I did baby the hell out of that car, changed the oil every 2500 miles..shouldn’t have texted while driving…) That being said, I’ve had 2 cars and 3 motors since then and they ALL sure do like to eat oil — though this one is the first one that does it without a huge external leak assisting in the uh..disappearance. (other times I figured it was just 100% leaking)

Reading up now on what exactly is piston ring sticking (sticking the the piston but not rubbing the cylinder wall — hmm learn something new every day) Didn’t know you could have something like that without compression loss, but I just read that if its the “oil control ring” that can be the case. (more news to me 🙂 )

How hard are the valve seals to replace?

[Author]

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