I own an 89 Honda Accord with close to 201000 miles on it. This evening I could feel it getting bumpy and needing oil, which when i checked was about 1/2 full (only 1 inch on the dipstick) and i put 2 qts of 10W-40 into it along with some power steering fluid (in the right places of course.) As soon as I started the car a tremendous amount of white smoke came billowing from the exhaust, which lessened gradually as I got it home, but the engine also is knocking when I release the gas above 2500 rpms. Any ideas what is causing this, what I should do to fix it? Thanks.