5w-40 vs 15w-40 startup smoke

[Skyco]

Thought I'd mention something interesting to me- I have a 96 f350 with the Powerstroke diesel and 180,000+- miles. Never has used any oil.
About 2 oil changes back I switched from 15w-40 to the Rotella 5w-40 oil.
At some point I noticed a pretty large oil smoke cloud on initial startup, especially if the truck had sat for a few days or longer. It would clear up as the truck warmed.
So last oil change I went back to 15w-40, in this case Delo.
Within days I noticed I no longer get the startup oil smoke...hmmm.
I've noticed for quite some time some external oil seepage from the turbo, not real messy but things stay a little "oiled".
The truck has never consumed enough oil between 4,000 mile changes to really even spot it on the dipstick. Next step is to clean up that turbo area oil and see if the seepage comes back. My theory is the thinner oil was seeping through the turbo bearings at rest and causing the startup smoke....or maybe seeping past valve guides into the combustion chambers.
In any case the startup smoke is gone and I like that, but it puzzles me...I guess the real test will be to go back to the 5w-40 at the next change and see if the smoke returns.

 

[DIRTROAD]

I would stick with what works and not take any chances.

A few years back I went to change the oil in my VW Golf diesel with over 300,000 on it. It was a very, very cold day and when I removed the drain plug nothing came out. I cranked it and drove around a few miles and came back and drained the oil, still very slowly though. I was using Castrol 20w-50 at the time. I decided that I had better change to something else because this couldn't be good for the engine.

Well, my logic was flawed. The engine didn't last long at all on the new oil that I used.

The moral of this story is: If it aint broke, don't fix it!!!

 

[Diamondpilot]

Why fix it if it aint broke??? I would stick with the 15W40 and leave it be. Sounds like you have a good old truck there so getting fancy will just confuse it.

Chris

 

[Skyco]

Yes it has been a great truck...I plan on keeping it for 500,000 miles just for grins...
Well I'm "stuck" with quite a few gallons of the Rotella 5w40 that I stocked up on.
Oh well, it works fine in the Kubota, the ATV, the motorcycle and the 4 stroke Suzuki outboard.. Of course all of them together only hold about the same as one change on the Powerstroke....oh I forgot about the lawnmower, log splitter, various generators etc...so it will have a use..

 

[Gale Hawkins]

5W is thinner then 15W is all I can think of. I have not seen that with any of the 4 changed to T6 but will keep and eye out for it.

Why are you concerned with the oil smoke on cold start up? Worn valve guide seals are not a real problem most will let some oil drain down when setting for a while.

 

[Skyco]

Why are you concerned with the oil smoke on cold start up? .

Cause it ain't supposed to do that
And doesn't when I changed to a different oil.:laughing:
I like my stuff "right".:thumbsup:

 

[Gale Hawkins]

Cause it ain't supposed to do that
And doesn't when I changed to a different oil.:laughing:
I like my stuff "right".:thumbsup:

How does masking the wear with heavy oil really change anything other than your pride.

If it smokes a little then you know it is getting oiled well.

 

[Skyco]

15w-40 isn't heavy oil, it is the RECOMMENDED oil by the MANUFACTURER.

EXCUSE ME for posting my observation- you are looking for an argument. Go somewhere else.
Please add me to your ignore list.

 

[Gale Hawkins]

I should have said "heavier" instead of heavy.

Natually a worn engine is going to use more oil the lighter the weight but it seems Ford went to 5W-20 for EPA reasons and not for better lube.

I think I see a tad bit more oil used with the Rotella T6 5W-40 vs the 15W-40 non synthetic but it does not require adding any in 3000 miles one the old 454 I know.

 

[RalphVa]

A 5w40 oil will be heavier at startup than at operating temperature. So, it's not a component in startup smoke.

Ralph