getting gas left truck running it was about 20 degrees outside, went to put 1 quart of oil in opened oil filler tube and it let off a good bit of cranckcase pressure added 30w oil because thats all the little gas station had that would be thick enough well soon as i added oil truck started too knock and smoke real bad so i shut it off quickly added some stp oil additive and restarted no knock know but still smoking bad it idle up on its own a couple of times but as soon as i touched the gas pedel it would idle back down when i let off drove it home luck would have it that my wife was with me we were filling both car an truck so she followed me home, it smoked all the way home aminly out of right side exhaust, wife said it looked like a small chunk of somthing came out of right side exhaust, wierd enough still had normal oil pressure through out and truck ran ok not great but ok not like a blown motor would. its an 82 gmc 6.2 1500 pick up with about 260,000 on it. mainly white smoke just if it matters please help

You didn't put GAS instead of diesel in it by any chance?

maybe a blown head gasket or some fuel issues. May have a waxed fuel filter or something. do you poor in any additives? try some stanadyne first to see if it clears up. i don't think it is a blown motor. get it to a shop to look at it. but before then, try replacing the fuel filter and check it again, after placing some fuel additive. the station you went to may have received a bad batch from the fuel truck.

Check the dipstick for signs of water in the oil.
How low is the radiator holding tank?

Hafta think you blew a head gasket. L8R

oil looks black just like allways, it had all of the same power its had just idled real roughim going to change the oil in about ten min to get the one odd quart out because as soon as i put that quart in it all went down hill then i will go for a fuel filter. thank you all for your help this is the first real prob this truck ever had

keep us posted as to the outcome.

Try removing radiator cap with engine off and then start engine. Look for low coolant and or bubbles. If coolant is low add some to fill it up, bubbles are usually a sign of a blown head gasket. If no coolant problems, put a heavy dose of additive in the fuel. You could have an injector that is dumping fuel. Try this and get back to us.

ok just found the reson for all of my issuse the other night with the 6.2 and the 6.5 you cannot put oil in it while it is running due to the fact of the oil drains on top of the timming chain and it will throw the oil back up the oil fill tube and what doesent get out goes into the intake manifold which caused the knocking and all of the smoke that is why the further i drove the better the truck ran. thanx for all of your help and quickness to answer my ?