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Engine's burning oil - how much longer will it last?

bottgersbottgers Posts: 2,028
I have a '93 Tercel with about 125K miles. It had 89K when I bought it back in '02. The engine used a little oil when I bought it (I had to add about 1/2 qt every 750-1000 miles or so), but I believe the consumption has gotten worse. Now it'll go through 1/2 qt about every tank full of gas. It doesn't leak so I know it's burning the oil. The weird thing is that the engine still runs very well, has plenty of power, and still pulls over 40 MPG on the highway. In other words, the engine doesn't act like it's burning oil as badly as it is. Usually when an engine shows signs of wear to where it's burning oil this badly, you usually notice a definite drop in power and/or fuel economy. That's just not my case. I've always used good oil (Havoline) and filters (PureOnes), with frequent change intervals (about every 4K-5K). I guess my questions are these: How much longer before this sucker starts looking like a misqusito fogger going down the highway, and is there anything I can do differently to slow down this wearing out process? Also, I was hoping to get 200K out of this car. Is that no longer a feesable goal?


  • MrShift@EdmundsMrShift@Edmunds Posts: 43,641
    I bet it's a fairly simple job...that's just a little SOHC isn't it? You could inspect the cam and possibly re-use it if it was expensive.
  • andys120andys120 Loudon NHPosts: 16,385
    Are you getting less than 500 miles per quart? If so you may have to replace the motor but if you are still in the 600-700 mile range then you might be able to get some more use out of it.

    It doesn't sound like you'll get 200k out of the motor but you could get that out of the car if you want to put another motor in it.
  • MrShift@EdmundsMrShift@Edmunds Posts: 43,641
    It's not uncommon for vehicles to burn oil but still run well. Old Volvos are notorious for this. Your oil rings are probably shot or maybe you are sucking oil through some really bad valve guides or seals.

    At any rate, unless you run afoul of emissions testing (which generally doesn't care how much oil you burn) or unless your car's smoke becomes reallly obnoxious, you can keep it running for a long time. Eventually you will burn oil so badly that you'll foul the plugs a lot or destroy your catalytic converter and this will become quite a nuisance for you.

    Or you will forget to add oil and then KABOOM.
  • fintailfintail Posts: 32,907
    That happened to my fintail, as it was stored for some time and the guts of the engine deteriorated. The plugs would foul, so I'd get to clean them and run it for 30 mins until they fouled again. The car eneded up getting a valve job AND was a disastrous job that took me and some others over 2 months to do. But 8 years later, it's running like a top.

    The worst it got before I had to break down and fix it was maybe 200 miles/qt on the highway, I could double that in town. Smoke was awful at startup or when going up a steep hill...barely notioceable otherwise.

    If you really like the Tercel...just have it looked at. A valve job couldn't cost too much on something like that...surely less than that fintail.
  • iluvmysephia1iluvmysephia1 Posts: 5,663
    the baby in on a new Scion xA RS 2.0, eh? I owned a '66 Ford Fairlane(without fins!!)that burned oil badly. When the smoke would waft inside the passenger cabin I finally had to get rid of the thing. Yukko. Talk about barbequeing your old car's engine!

    fintail, been to Burlington, WA lately? Anything new along the I-5 corridor there?

    BTW-take a gander over towards Burlington as you're heading past town on I-5 next time and you should be able to spot Jerry Smith Kia there on old Highway 99. That's the dealer I bought both of my Kia's from. They're a solid and reliable dealer of Kia products there in the beautiful Skagit Valley region of Washington state. Over and out.

    2008 Mitsubishi Lancer GTS

  • bottgersbottgers Posts: 2,028
    Here's what I'm thinking on the matter. Since the engine's still got good power and it still gets good fuel economy, my guess is the oil burning problem isn't coming from worn cylinders or rings. I would say this indicates the engine still has good compression which means the rings, cylinders, and valves are all sealing properly, which could only mean the valve guides are the cause of the problem. Anyone else agree? If this is the case, I could have the valve guides replace relatively inexpensively and still have plenty of miles left on the car. I really don't want to replace the car just yet if it can be avoided.
  • MrShift@EdmundsMrShift@Edmunds Posts: 43,641
    You could have worn oil rings but good compression rings however.

    Best way to know what's up is to do a cylinder leakdown test, and then all will be revealed.
  • fintailfintail Posts: 32,907
    My fintail had a severe lack of power and poor mileage when it was an oil burner. I was amazed at how competent the car performed when I had it fixed...the mileage isn't shabby either.

    iluv - I now live in Bellevue, transferred to a better job. I'll actually be going through that area tomorrow though, to pick up the fintail (it is stored north of Bellingham) and bring it here.

    Do a leakdown test for sure, as Shifty says. A valve job for that thing has to be well under a grand.
  • chrisducatichrisducati Posts: 394
    My daughter drove for about two years using a quart every five hundred miles. as long as it isn't blowing blue smoke and you keep it topped off it will run for a long time. She just checked the oil every week and added when it reached the Add point. That was a Nissan Sentra that had maybe three oil changes in 100000 miles... I think it would have lasted a few more years had it not been totaled. And a lot longer had she changed the oil.
  • bottgersbottgers Posts: 2,028
    So is it possible the problem could be worn valve guides? If that's the case, I'm thinking that couldn't very expensive to get fixed, right? If it's the rings causing the problem, then that would be something I'd just have to live with. I wouldn't spend the money it would take to rebuild the engine. I suppose a valve job would be worth doing if the rest of the engine is still in good shape.
  • MrShift@EdmundsMrShift@Edmunds Posts: 43,641
    Well doing a valve job on top of an old engine can be tricky business. Now that your internal engine parts are used to chuffing along like a low compression locomotive, to be suddenly subjected to a very tight top end may pound the bearings and rings into submission.

    This is why you want to do a leakdown might have both valve guide AND ring wear, in which case strengthening the top end will only cause more oil to escape past the oil rings into the combustion chambers.

    Testing for bad valve guides shouldn't be too hard. First of all, if your valve guides are the culprit,'ll get a lot more blue smoke at start up, and it will gradually diminish; also, if you get blue smoke while ACCELERATING, that's usually rings...if you get huge clouds of blue smoke while DECELERATING, that could be guides. So when you get a high vacuum situation (closed throttle plate) you'll tend to suck oil past the guides, but in a low vacuum situation (throttle to floor) you'll tend to pump oil through the oil rings.

    Another sign of bad rings is blow-by, which is that chimney smoking effect you get at idle, where you can see puffs of smoke coming through the oil cap on top of the engine---be careful about testing for this on OHC engines, as the camshaft can send a lot of oil through the open oil cap.
  • chrisducatichrisducati Posts: 394
    so isn't it fairly expensive for either of these. Valve guides or rings. We had a toyota that the rings went bad at about 140000 miles, I couldn't get anyone to re ring the car and that engine was not available from a remanufacturer. Seems the thin cylinder walls meant no over bore. I doubt I would put 1500 bucks in an old toyota.If that is all the car is worth to begin with.
  • bottgersbottgers Posts: 2,028
    My car has exibited one of the symptoms you listed which is the puff of smoke coming out of the tailpipe during startup. The only other time I've actually seen the engine smoking was the other night. I was leaving a parking lot after a fireworks display and through the headlights behind me I could some smoke coimg out of my tailpipe while the engine was idling. As soon as I brought the engine above idle, the smoking stopped. I haven't seen the engine smoke during acceleration or deceleration, nor have I seen smoke coming out through the fill hole. I guess like you said, probably the next move would be to have a leakdown check done. I have that before about doing a valve job on an old engine and that it can cause problems with the bottom end. I guess at this stage of the game, the only thing I would probably want to do would be to replace the valve guides. Anything else I'll just have to live with until the problem gets so bad it isn't worth dealing with anymore.
  • bottgersbottgers Posts: 2,028
    I could be wrong about this, but I would think having the valve guides replaced would be the least expensive thing to fix of all the possible problems. If the rings are bad, that would mean a complete engine overhaul and I wouldn't do that as it would be prohibitively expensive.
  • MrShift@EdmundsMrShift@Edmunds Posts: 43,641
    If your leakdown test determines most guide wear, I'd just order up a rebuilt cylinder head from a rebuilder and slap it on there rather than rebuild yours.

    Lookee here---only $285 bucks. I couldn't buy even the valves alone for my engine for that.

    PS: I have NO idea if these are any good---I just googled 'em.
  • chrisducatichrisducati Posts: 394
    that isn't to bad a price. Add the price for the new cam, seals and labor, it might be worth it. Depends on what the rest of the car is like.
  • geo9geo9 Posts: 739
    You could have a simple problem............Bad PVC valve or if you have power
    brakes...... a bad vaccuum line to/or brake booster check valve !!!!

    A cyl. leakdown test as others have posted will tell.......................
  • bottgersbottgers Posts: 2,028 valve guides or something even less minor, I'd go ahead and have the work done. If it's going to get into things like replacing the head, valves, canshaft, or bottom end work, then I'll just keep driving it as is. It's probably not worth spending a grand or more to fix the problem. I will have the leakdown test done and see what the verdict is.
  • geo9geo9 Posts: 739
    With these OHC engines everyone RAVES about being so modern
    and such there is NO minor repair of the valve guides.

    Major disassembly is required as well as machine shop work which
    is quite spendy. Not to mention the added parts that may be required
    since you already have a 100k mile engine. (Timing belt, cam seals,
    water pump and on and on)

    Run it till it blows up and save yer money !
  • MrShift@EdmundsMrShift@Edmunds Posts: 43,641
    That is my inclination....however, you could possibly replace the valve stem SEALS without disassembly. You could also run a heavy straight-weight oil and that might help some.
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