Losing lots of oil–at least 5 quarts in two months–with no oil on the ground, at least not where we park at home.
However, we haven’t detected any smoke coming out of the exhaust.
But what else could it be, if anything?
(And how long does an engine rebuild generally take btw?)
It could be valve seals which are much less expensive. Let the car idle for several minutes then give the engine a rev and see if it puts out a good puff of smoke. Or check for smoke when car is first started.
it would really help if you’d say what car and engine you have.
Check the valve covers for leaks.
Best guess with the little info you gave: leaky valve seals.
Is your tail pipe noticeably encrusted with blackened gunk?
Year, make, model, engine size, total miles, miles driven in the 2 months mentioned on the OP will be a good start.
Until we have some facts all I can do is guess.
So here is my guess: it’s not lupus. It’s never lupus.
Out of curiosity, what difference does the make and model etc make? Like depending on different answers to that question, how would it affect your ideas of what is going on?
In this case, it’s a 2001 Ford Windstar, 120000 miles, I don’t know the engine size and would estimate 700 miles driven in the last two months.
5 quarts in 2 months is 30 quarts a year. 30 quarts at $3 is $90 a year. Engine rebuilds cost serious money, so it would be cheaper to just keep pouring oil in–assuming there aren’t any other problems.
It is.
I had the idea that this is the kind of thing that gets catastrophically worse if you keep driving the thing. Not so?
Go find a hill to coast down with the engine running and in gear. Then step on the gas sort of hard at the bottom. Does it smoke now?
Have a compression test run on all cylinders.
Seriously?
Well, for one, with the type of question you’re asking knowing the make/model/year helps in case there are any common problems which would apply to your situation. E.g. If you had a late '90s Chrysler vehicle with the Mitsubishi V6, we could immediately say you’re burning oil because the valve guides are shot.
What does the coolant and oil in the engine look like? You have the 3.8 liter Essex V6 which has a reputation for blowing head gaskets (see why we asked for make/model/year?) oil could be seeping into the coolant passages or vice versa. Have it looked at, neglecting failed head gaskets will guarantee the need for a rebuild or new engine.
Yes, seriously? 
Thanks for the example, that makes sense.
I will.
Plug all the data in to get an estimate for the value of your vehicle:
http://clearbook.truecar.com/
What number do you get? $3,000 or so? Most people don’t recommend spending a huge amount of money on repairs on a low value vehicle.
But hopefully an expert will show up and comment.
Last time I checked it was worth about $1500, if the buyer’s being generous.
Even if it turns out to be a rebuild, the $3000 for that (per estimate given to me by a local rebuild specialist) is a lot less than the $15000 to $20000 I’d be spending on a new vehicle that meets my needs…
Somebody here on the dope once talked me down from getting a new one during a previous problem, pointing out that maintaining an old car is, even over time, cheaper than buying new ones every time a repair cost goes over a car’s value.
It would be cheaper and easier to buy a used Windstar than to rebuild the engine.
what does the oil in the engine look like? does it have the color of coffee with milk in it? also check the coolant in the radiator (obviously do this when the engine is cold.) does it look like it has muck floating around in it? Either of these could indicate a bad head gasket which, while not cheap, is far less than an engine rebuild/swap.
also, try this. When the engine is warmed up and running, remove the oil fill cap. Is there a ton of vapor coming out? also see if there’s oil in the air filter box/intake duct from the PCV system. this could indicate excessive blow-by, which would mean an engine rebuild eventually.
Hm, I haven’t seen this to be the case from reputable used car dealers, (and to be clear, of course I was looking for used vans in general not just this particular model) but I’ll keep looking if you’re sure.
I mean what I’m thinking right now, but could easily have my mind changed, is that if it needs a rebuild, the choice is between spending three thousand dollars once, or potentially three to five thousand dollars over and over again in search of that extremely cheap used van that won’t break down in six months.
Huh… maybe I entered some value wrong last time or something… just searched again to find representative examples and I’m now finding plenty of vans like what I’d need in the $1500-$4500 range… some from dealers with, at least, lots of good consumer ratings (though I don’t really know that this is that great of an indicator.)
Welp, maybe a thread coming soon asking for advice on how best to buy a super cheap used vehicle… like if i know nothing about cars, how do I ensure I’m getting something that will stay on the road for a few years?
Frylock, you can easily check to see if it is rings are valve seals. Big difference. You don’t even need tools.
You’ve been given some good advice here so far, let me recap:
[ol]
[li]Check for the tell tale signs of a blown head gasket by looking for a milky frothiness in your radiator or coolant expansion tank. No cost for this check. You don’t want to see a mucus like nasty consistency to your coolant. This in one time you do not want a latte.[/li][li]Buy a compression gauge from your local auto parts store. They are cheap, less than $20. Go online and google what your compression SHOULD be, and find a tutorial for how to do it on your engine, Requires removing the spark plugs, so you’ll need the right sockets for that. You want to have all 6 cylinders near the correct spec, and all within a tight range of each other. I did this just yesterday on a 4 cylinder Honda engine. Online research told me that ideal was in the 180-185 PSI range. My results were 180, 182,182,181. Which is fine. Actually great for an engine with 248K on it.[/li] When you do the compression test, do both a dry and then a wet test of each cylinder. Again Google is your friend. A big jump in compression with the wet test tells you your piston rings are worn out.[/ol]