I have a 2008 speed 3 sport hatchback 90K miles, always serviced religiously at the dealer, which is now going through 1 quart of oil every 500 miles. There are no leaks externally and the car does not smoke at all. The dealer doesn't seem to know what the problem is. In fact they gave me a gallon jug of oil and told me to keep an eye it.
Is this common? and if so is there a cure?

 

LOL

Your last line was funny sorry!
Ok so oil just does not disappear, you either are leaking it or burning it. The consumption you claim is a lot.
Spark plug will tell if you are burning it. Pull a couple and have a look. Post some pictures.
I would be doing a compression test and followed up by a leak down test which will tell you the health of the engine. The shop should have at least done that IMHO?
Leaking oil... I am dubious that anyone gave the engine a complete inspection on this one. The age and mileage you are sure to have some leaks not to the degree of your problem but no mention of any??? hmmm??

 

I agree it is almost comical, and I am talking about a super schmansy Mazda dealer not some shade tree mechanic.
the reason I say it doesn't at least look like its leaking is because it is garage kept and the floor is completely dry. Not a spot! So consumption is the likely candidate it must do it very efficiently as I see zero smoke. I will pull a couple of plugs and check their condition. I do periodically get a check engine light for air mixture?

 

I had this same EXACT problem but with an older Toyota Camry. The dealer could not find anything. I went to a local mechanic. Nothing! I had to fill in a quart every month or so and there were no leaks. A friend who had a Mustang, cant remember what year it was, but he had the same issue and used Amsoil and it stopped the consumption completely.

I tried it and it stopped the consumption by 90%!! I was tired of keeping an eye on it so I said what the heck. Never used another oil since. I use it for my 2016 Mazda and another vehicle. Only change the oil once a year.. I looked up your vehicle, if you are interested in trying it out then here is the link:

https://www.searchforparts.com/oil-c...2.3l-mzr-turbo

can't hurt, it's a solid oil, but it's up to you.
Mike.