Eating up oil but no visible leak on the driveway or underneath

Oops! Sounds like your engine block is cracked,or your engine heads are warped, or you need new head gaskets. The cheapest problem is the last one. However it still is not cheap. Most head gasket sets cost at least $100 or more. To see if you need head gaskets, after running the car for about 15 minutes, pull out the oil dipstick and see if you see oil or water bubbles on the stick. If you need head gaskets check ebay for your model, that's likely going to be your cheapest source. Also possibly the engine blocked is cracked internally. That explains the loss of oil AND coolant out the pipe. But this also comes with overheating, so if your car is not overheating then this may not be the problem. First advice: BE REAL CAREFUL! CONSTANTLY STOP TO CHECK AND ADD OIL AND COOLANT until you fix the problem. Another advice, take your car to a reputable repair shop and have the engine pressure tested for leaks to find the source. WARNING: Do not use engine block leak sealers, they mess up a lot of stuff on your engine, especially the radiator heater core.

If you were in the states, I'd suggest you go car hunting. multiple problems like this usually indicate (over here) that a vehicle is on it's last legs. since your not spotting anything major, you may only be burning oil. the engine may be about shot, and need a Ring Job. have someone peek at the radiator, hoses and water pump...it may be gone. if the car has blue smoke, you are definetly burning oil

I have a focus 03 lx 1.6 i also have oil problem it needs topping up about every 6 weeks,about a half litre,i took to a ford dealer who done a pressure test,he said there was no problem with the engine,the engine is completely dry and so is my garage floor,it's not smoking and has plenty of power,checked oil cap no sludge