have a 1997 Nissan pickup with 269000 mile on it when you first crank it up after sitting all night a puff of blue or white or gray smoke come out of the tail pipe. anything in a can will help.
That’s probably from slightly leaking valve seals. If you’re not using much oil, I wouldn’t worry about it. You could use ‘high mile’ oil, it swells rubber parts, it might help.
Texases is 100% correct on all points.
Short of replacing the valve stem seals, the only possible cure is to switch to high mileage motor oil.
If the OP wants to try something prior to the next oil change, there are some miracle in a can products that can also help to swell the engine’s seals slightly. If you browse the additives aisle at Auto Zone or Pep Boys, you should be able to find one of these products.
So if you have worn valve stems and worn valve guides, “good” valve stem seals will prevent oil seepage into cylinders?
Depends how worn the guides are. But new seals would help. Often it just the seals that get old and hard, no longer sealing very well.
While agreeing about the valve seals, another possibility is that at 269k miles the piston rings (and especially the wiper rings) could be worn When the engine is shut off there is still oil clinging to the upper cylinder walls due to the worn/stuck wiper rings not doing their job.
The oil has a tendency to pool on top of the pistons and upper compression rings and ergo; once started that minute amount of oil goes out the tailpipe in a whisp of smoke.
Granted, the amount of oil is negligible but enough to be noticed.
Given the age and miles of the truck, any ring replacement would not be economically viable so to speak. Valve seal replacement could be but seeing as how there is no test for that problem it’s a bit of a pricy guess if you’re paying to have it done.
After 269,000 miles, that puff of smoke might be the engine just taking its first morning breath happy to be alive. Sometimes I wake up like that too… {
Seriously, I agree with the above posters. Valve stem seams that leak slightly, and rubbery bits do that when the get old, allow some oil from that which lubes the camshafts to drip down on the backs of the valves and (if the valve is open) into the cylinder. It gets drawn in when you start the engine and burned. It’ll also get drawn in during deceleration, when the vacuum in the cylinders is very high as the pistons try to pull air through a passage blocked by the closed throttle plate.
And there’s also OK4450’s point, which I cannot improve upon the description of.
The condition can reduce the lifespan of the catalytic converter by allowing oil fumes and smoke out the exhaust and onto the catalytic coating, causing it to be ineffective, but other than that it really isn’t a problem other than a sign that your motor is getting old. If the valves are readily accessible and you’re up to the job, you might consider doing the valvestem seals. I don’t know that I’d personally do the rings (an engine rebuild). That might be analogous to swatting a fly with a 3 pound sledge.
There isn’t anything that will prevent that initial puff of smoke. The forty weight oil I used in a 73 Maverick would stop the constant smoking but didn’t prevent the initial cloud on startup. The 302 is a different engine, but all things being unequal, canned stuff may do nothing for the initial puff.
Our 1984 Chevy Impala with the 305 engine had this smoke puff on start up. My son drove the car from 1996 till he finally sold it when getting his first new car. By that time it had 300,000 miles on it and the smoking had not gotten worse.
The valve guide seals did not affect the emission test, always run with the engine hot.
Thank your lucky stars that the pickup can even start at 269K. A lot of vehicles with way less miles can’t make this claim. Grandma is slow but she is old.
I know of something cheap in a bottle that will help. It is called motor oil, add as needed.
