Geo Metro burns oil - solutions

geo
metro

#1

My '91 Geo Metro burns a LOT of oil. I have discussed this with several people, who have posed a few different solutions. Here they are:



1) Use a heavier oil. I traditionally used 10w-30 for better gas mileage and better starts in cold Wisconsin weather, but some have said that switching to 20w-50 will help slow the flow of oil past the seals, thus burning less.



2) Replacing the seals may seem like an obvious solution, but the Metro’s 1.0L I3 engine is made entirely of aluminum and prone to warping. I drive it very gently, but the last owner was not so careful - I suspect that replacing the seals in an already warped engine will not help much.



3) Crankcase additives promise to eliminate oil loss and smoke, some even say they will do it permanently. Do any actually work?



What are your thoughts?


#2

What is “a LOT of oil?” How many miles per quart? This matters.

How many miles on your Metro? This also matters.

  1. I do not recommend “heavier oil.” If the engine is burning oil, the engine seals have nothing to do with it. Burning oil means the piston rings are worn.

Seals prevent leaks at things like the crankshaft, the camshaft, etc. Seals prevent oil from leaking from the inside of the engine to the outside of the engine. Worn seals can leak oil, but they don’t burn it.

If the engine is burning oil the rings are the problem, not the seals.

  1. “Warped engine?” What the heck are you talking about? There are certain thing that might warp. The aluminum cylinder head is one of them, but you’re not describing symptoms of a warped head.

Forget this “warped engine” theory. It’s not the problem, either.

  1. NO!

Additives are a waste of money. NONE of them do anything.

So, back to square one. How many miles on the car, and how much oil is your Metro burning? Does it leak oil? If so, how much?

Have you tried replacing the PCV valve? A bad PCV valve, which is cheap to replace, can increase oil burning when there’s nothing else wrong.


#3

The engine in the Geo Metro is not entirely made of aluminum. I should know because I had one apart for a year and the cylinder walls rusted.

If you have a bad crankshaft seal, your car would be leaving oil puddles in your garage. Bad valve stem seals can also cause high oil consumption.


#4

I agree with you mcparadise. The only point on which I would like to comment is the one about additives.

Purchased separately, additives are a waste of money. However, Amadameus might try an oil with a different additive package already in it, like a “high mileage” oil. It couldn’t hurt to try.

Amadameus, replace the PCV valve, let us know how much oil is being burned, and give us the current odometer reading.


#5

I’d switch to high milege oil and find some additive that says reduces oil leak. There is nothing in a can or bottle that will “rebuild your engine”, but there are additives that have chemicals that will “swell up” seals, thus slowing down the leaking. Understand this is not a good ‘fix’, but if you just want to get by in the most inexpensive way, without doing any major engine work, then I’d take my advice above. It will only work temporary, then eventually your leaks will come back and probably be as bad as they were before, but the doctor in a bottle might provide some temporary relief, as least enough to get the environmentalist off your back for leaking all over the ground.


#6

Thanks very much for the helpful advice! Here’s the information I have:

The engine has 102K miles on it, and if my records are correct then it burns almost three quarts per gas tank, and each tank goes about 225 miles. (This is significant, because I’m paying $18 for a tank of gas and almost $10 in oil!)

I can confirm that it does not actually LEAK any oil, it’s stored in a clean garage and has not marked its territory. When I start it up there is often a small cloud of blue smoke, but this is the only time I see any sign of oil burning whatsoever.

Even more frustrating, I changed the oil immediately after buying it. I am not due for a change for another 1,000 miles - and yet the dipstick is sludgy and black.

(Edited for grammar)


#7

I wouldn’t use a heavier oil. All this does is starve the engine of proper lubrication at start-up causing more engine wear.

You might try this product http://www.restoreusa.com/Engine_Restorer.html
I’ve used this in engines that burned oil because of worn piston rings. And if it didn’t totally stop the oil burning, it reduces it significantly.

Tester


#8

Your engine has serious internal issues. Likely worn rings and leaking oil into the cylinders via the valve guides. I don’t believe a bad PCV valve or screwed up vacuum lines could burn oil this fast.

I suspect you don’t want to spend the money on a rebuild of this motor or even a change it out for a used motor from a salvaged car. 3 quarts of oil per tank of gas must mean a whole lot of blue smoke follows you everywhere. This should kill your catalytic converter off soon too.

Why not try an additive, it can’t hurt a motor that’s pretty much on its last legs as is. Continuing to drive this car this way is an envoirnmental nightmare. Either fix it or junk it, but it is irresponsible to keep driving it as is.


#9

You are the second owner. Are you sure it doesn’t have 202K or even 302K miles on it? The '91 models only had a 100,000 mile odometer. I put 280,000 miles on my old '91 before retiring it and it still wasn’t burning that much oil.


#10

I have to agree with those that suggest that this 18 year old engine is just plain worn out. While oil rings and compression rings are different parts, I suspect that a compression test would confirm that it’s just plain old tired.

You could try some oil system flushing additive. Follow the instructions on the bottle to the letter. In addition to wearing, rings also lose their spring tension over time. If they’re also gummed up then flushing them out might help. It’s a longshot, but a cheap try worth trying.

While heavier oil is worth a shot for lost oil pressure at idle, I’m not sure it’d help something burning that much oil. But, with respect to the engine’s top end needs, I’d be inclined to try it. You may have so much wear now that it can get into those tight spaces and lube the top end sufficiently.

Additives in general are a bad idea for engines that are running well, but for an old engine that’s worn oout anyway they’re worth trying.

In summary, flush it out and try a heavier base weight oil. Post back to let us know how you make out.


#11

Oil burning is going to be due to rings, valve seals, or both.

Valve seals (no test for that) is a doable repair. Piston rings (compression or leakdown test may help verify this) means an engine overhaul.

The mileage on the vehicle is low and in theory should not be going through oil that fast.
My feeling is that there’s a history of overheating, lack of regular oil changes, or both; with the former being most likely. Overheating will kill piston rings and valve seals both.

If the engine oil level was at the FULL mark when you bought the car you now know the seller was likely aware of this problem and decided to dump the car on an unsuspecting person.


#12

If you’re not leaving puddles, your engine is toast. You can try an additive, can’t hurt, but expect nothing. 70 miles/quart is EXTREME.


#13

Thanks everyone for the great advice - I’m talking with someone now who has promised to open it up with me and check the PCV valve and rings. I’m a little disappointed, but there will always be more cars out there.

Thanks again for the help!


#14

Any way you can run a compression test? If compression’s good (not likely), then it is something other than a worn out engine.


#15

Unless I read this wrong, you do not blindly open up an engine for a piston ring inspection. Once opened this means an overhaul whether you want it or not.

Check the PCV valve first and if that’s ok then go with texases’s advice about a compression test.
Run the dry test first and follow that up with a wet version of the same test.
A wet test simply means repeating the process one cylinder at a time after giving the cylinder being tested a small squirt of motor oil.
If the pressures go up considerably the rings are shot.


#16

These engines go into a death spiral once the valve seals become hardened by heat at about 100,000 miles. Oil leaks into the combustion chamber & sticks the rings, causing even more oil to blowby. Then carbon deposits onto the exhaust valves and they burn, causing the affected cylinder to stop firing. Your EGR channels will also be totally clogged with soot.

THE ENGINE IS NOT WORN OUT. IF YOU DO NOT HAVE BURNED VALVES, you may be able to (best case) replace the valve seals (perhaps even without removing the head) and unstick the rings with some kind of additive.

I had burned valves in mine – but the original honing was still visible on the cylinders with no detectable ridge. I replaced the exhaust valves, valve seals, rings, main and cam seals, and now at 170,000 miles I get the usual Metro mileage (about 45 mpg) and the oil stays clean for 2K miles.

Persevere – these are great little cars and should run a LONG time if you know the tricks.