2000 Corolla VE Excessive Oill Consumption

[Farbie]

My son has a 2000 Corolla that he bought used at 30000 miles. The auto now has approximate 70000 miles on the odometer. Prior to the last oil change he did 3000 mile oil changes at Jiffy Lube (against my advise).Unfortunately he never check his oil level between oil changes. He went on a 400 trip and the oil light came on. He was 3 quarts low. We did a complete oil and filter change (Castrol 10-30) with a Toyota filter and a new PCV valve. The auto continues to use oil particularly at 65-70 MPH. He just came back from a 400 mile trip and used 1 1/2 quart of oil. There are no apparent oil leaks and no obvious blue smoke coming out the tailpipe. Fortunately it is a certified used car from toyota and should be covered under the extented warranty.. I would appreciate any insight to what is causing this problem and the tact he should take with Toyota dealing with this problem

 

[H2GURU]

There have been several threads on here about Corollas using oil in excessive amounts when driven consistently over 70 MPH. No reason is given however. Some years it is printed in owners manual.One of the cars in my stable is a Corolla but I have not noticed any oil missing.