I have a 1990 Soverign, 4.0. Runs nice, getting 15/27 mpg. Noticing what seems to be excessive oil consumption. I'm thinking at least 1 qt. per 1k miles. Is this excessive for these cars? It is not leaking anywhere. I had a leaky rack n pinon, but I replaced that, now it does not leak a drop. The tail pipes look clean, too. The car has 123k miles. I was thinking of sinking some money into it, as I am growing fond of the car. I already have actually. New tires, '97 16" rims, fixed the air, and rack, and thinking of bushings, and what not. Any thoughts? Thanks.

 

One quart/1000 miles is borderline. Not horrendous but could be better. I'm guessing it didn't have the best of care in it's earlier life but who knows. After all, 123k miles ain't young by any means.

Years ago one quart/1000 miles would've been "normal". Depends what yer used to, I reckon. I had an MG that used a quart very 200 miles :-).

OTOH my XJR with 100k miles uses one quart/4000 miles.

Do a compression test and/or a leakdown test and post back.

I'm guessing worn rings/cylinders but it could be valve guides, too. It may soldier on for years without getting worse.

Cheers
DD

 

If it is just worn components, you may find that switching to a heavier grade of oil helps substantially.

20W-50 Castrol
15W-40 Castrol Diesel

are good bets.

 

You are correct that she did not have the best of care. It was my Mother in Laws car, and she loaned it to alot of people, on a extended basis, sometimes. (children) Trying to keep her alive cause my wife wants to keep it around. (sentimental) I am using 10/40 wt oil for now. Next change I'll go heavier. Was thinking of Amsoil. Kinda expensive to just blow it by the rings. When I get time, I'll do the compression test. Maybe leak down. We'll see. Thanks for the responses. Cheers

 

tinman,

Here's one thing you might try. I did it to my '93 XJ6 at 130K miles when it was using a qt. in 900 miles. GM has a chemical they used to call Top Engine Cleaner, they have changed it now to Upper Engine and Fuel Injector Cleaner, part number 88861802.

• Run the car and get it hot, park it in a safe spot, NOT IN A GARAGE.
• Remove the spark plugs and pour an ounce and a half of the cleaner in each cylinder.
• Let the car set for a solid day so the cleaner can work on the carbon in the rings.
• Cover the engine with an old sheet or something so when you crank it over, any cleaner that spits out is caught and doesn’t make a mess or get on the paint.
• Crank the engine over for several seconds to expel any remaining liquid cleaner.
• Sop up the top of the engine and cam cover.
• Reinstall the spark plugs.
• Start the engine [be prepared for some smoke, that’s why I say NOT IN A GARAGE].
• Take the car out and once it’s warm, run the dog sh** out of it to clean it out.
• Change the oil and filter IMMEDIATELY.

Once I’d done that the oil consumption was 1 qt. in 1800 miles. I was happy [well, content] with that.

This will help if the consumption is due to the sticking rings. If nothing is gained, then the oil is going down the valve guides or something like that. It’s not terribly costly, so it’s worth a try.


Good luck!