why is oil burnign up so quickly
 

I don't have this problem in my car, usually when I do an oil change and do the 5-6 quarts of oil there is enough oil in there till the next change.

However my brothers car, which is a very basic hyundai, burns up oil like crazy, there is no sign of a leak, He DOES drive a lot, it's a small engine though like 4 cylinder. He claims it goes through 1 quart a week...can anyone explain this? he uses 10w-40 would another weight be better?

thanks.

how old is the car? test the compression in the cylinders. im guessing theres a poor seal.

It's either rings/piston/cylinder bore or valve seals/guide--as suggested doing a dry, then a wet, compression test will tell you which.

Another indication is that smoking on heavy acceleration is generally a ring/cylinder problem, smoking on closed throttle deceleration (with a manual transmission) is generally a valve seal/guide issue.

However if that quart he's using is over 500 to 1000 miles is may not smoke badly, small hot-running engines can burn it up and just get a funny smell to the exhaust..