Buring Oil vs Flashpoint =Smoke?

[landtoy80]

With a motor that burns oil at start up or while driving, would an oil with a higher flashpoint make less smoke?

If you have an oil with a FP of 354 F and another at 519 F, would you notice a difference in the amount of smoke from the tail pipe? Or is the temp in the combustion chamber so hot that it doesn't matter?

 

[JAG]

Good question. It has to make a difference. How much difference is what's unknown. A good test would be to use Red Line and see what difference it makes.

 

[landtoy80]

Yes, Redline 5w50 is 514 FP oil and Toyota/Chevron Supreme 5w30 is 354. I had Chevron and it smokes at startup. Running G-oil 5w30 and its 430 F FP and it smokes.

I guess there would be a lot of variables like how much oil is leaking into the cylinder. I assume a heavier oil would leak slower that a light oil. How long the vehicle has sit. How hot the motor was when shut off...

 

[NateDN10]

In cylinder temperatures are much hotter than even 519F. Either oil will burn.

 

[Jim Allen]

If you are burning oil to the point of making smoke, a small difference in flashpoint won't make much difference in the amount consumed. It's a mechanical problem and oil can't put metal back onto worn parts. Once the oil gets into the combustion chamber, it's history. A high flashpoint may actually make more smoke...

Here's an interesting anecdote. Some years ago, when people first started putting their used motor oil into the fuel tanks of their diesel trucks, they found that some high flashpoint Gp IV and V oils wouldn't burn unless the engine was really making heat. At idle or startup, or any time combustion temperature was n[t very high, they would spit unburned oil out the tailpipe if too much motor oil was added to the fuel.

Lived in GJ for 10 years up on Orchard Mesa.... back before it was "Californicated."

 

[landtoy80]

Thats good to know that the FP wont make a difference.
Looks like I might want to try one of the Smokeless oils from Entek or FHS.

Just not sure how good either is for a motor that doesn't burn oil at operating temp. 1qt per 2000 mi.

 

[JAG]

Jim, your anecdote indicates that it's NOT true that once oil gets into the combustion chamber that it's going to fully burn. Oil only burns in vapor form so low volatility oils will vaporize and burn less. I once made the mistake of using a Maxima ester 2-stroke oil in my VW 1.8T's gas as an upper cylinder lubricant. It ended up being so resistant to burning that the spark plug threads become covered in the oil.

 

[Jim Allen]

Originally Posted By: JAG
Jim, your anecdote indicates that it's NOT true that once oil gets into the combustion chamber that it's going to fully burn. Oil only burns in vapor form so low volatility oils will vaporize and burn less. I once made the mistake of using a Maxima ester 2-stroke oil in my VW 1.8T's gas as an upper cylinder lubricant. It ended up being so resistant to burning that the spark plug threads become covered in the oil.


I believe that's what my anecdote stated... that the oil won't always burn. I didn't go into any detail, however. Of course a low volatility oil would burn more easily than a higher one but the point is once the oil gets into the combustion chamber, it's going out the tailpipe one way or another.

I am surprised to hear that a 2-stroke oil, which is DESIGNED for combustion, wouldn't burn in your VW. Did you overdose it perhaps? Recent testing has shown, in older diesels at least, that 2-stroke oil is a great lubricity additive (for pump internals and injectors) and only marginally less effective (though drastically cheaper) than the purpose made lubricity fuel additives on the market.

As I think about it, I would question the usefulness of adding an "upper cylinder lubricant" anyway as they would generally just add to combustion chamber and intake valve deposits. But there may be some VW specific issue you know about that I don't which is addressed by an additive like that.