A engine that have blow by and burn oil is bad? engine run great,good fuel economy but blue smoke come out from the tailpipe whenaccelerate?

You could have sticky or stuck piston rings. It may only be 1 or 2 cylinders bad, not all of them. Pull the spark plugs and look for the ones with black oily tips. As for now, you could run thicker oil, say 10w40 or straight SAE30 or HD30 oil, etc. There are several tricks and oil treatments used to clean up the engine interior though. I have had good luck pouring a can of seafoam gas treatment into the oil and drive it for about 30 miles, then change the oil & filter. You can see online videos, etc in reference to similar results

Your engine has internal wear. More than likely the cylinder rings are worn along with the cylinder walls. Engine was probably neglected and oil/filter were not changed regularly. It can lost for many more miles in this condition. Unless it is burring lots of oil just keep driving it and be sure to cheek the oil regularly. The only fix would be a complete engine rebuild.