Oil change syntetic-> mineral

Rayho · 12-26-2018, 11:33 AM

Want to go back to a quality mineral egine oil after syntetic oil leak. But as I understand I will not get all the oil out on a normal oil change. Is this a problem, with the mix of oil? It will be a couple of liters syntetic oil left in the system.

full quack · 12-26-2018, 12:36 PM

If you break the lines loose at either the thermostat housing or the front oil cooler, you can get damn near all of the old oil out of the system.
But with that being said, a couple of quarts/liters of synthetic oil won't hurt a thing, and that will get largely diluted with each subsequent oil change down the line.

You made a comment awhile back about being concerned about the type of oil to use vs. the possible impact with a catalytic converter. I know that you have determined that you have no catalytic converter now, but the truth is that oil type does not come into play with a CAT, it is the type of fuel you run instead...leaded vs unleaded.

Mark

Noah930 · Noah930's Garage

Not to contradict you, Quack, but I was under the impression that oil can affect the catalytic converter--but in the detergent package/additives. I think that's the reason why over on the technical forum, they have that epic thread on oils. Zinc has been diminished from oil additives due to shortening the life of cats. That may have a detrimental effect on flat tappet valvetrains. So the air-cooled guys have been trying to find oils with high zinc content. Doesn't matter if that is mineral or synthetic, though.

speednme1 · 12-26-2018, 05:02 PM

Quote:

Originally Posted by full quack

You made a comment awhile back about being concerned about the type of oil to use vs. the possible impact with a catalytic converter. I know that you have determined that you have no catalytic converter now, but the truth is that oil type does not come into play with a CAT, it is the type of fuel you run instead...leaded vs unleaded.

Mark

Not necessarily true, certain formulas of zddp allow more hydrocarbons to settle in the oil thus extending the life of the cat.

quattrorunner · quattrorunner's Garage

Cat? Are you serious? Ditch that cat!

Rayho · 03:17 AM

No I dont have a cat.. I will try this MPM Classic High Zink mineral oil.
We only have unleaded fuel in Norway

T77911S · 12-27-2018, 03:48 AM

fix the oil leak and keep using syn.
its waaaay better for the turbo, and engine due to turbo heat.
the other thing is coking in the turbo. you stand a chance of your turbo coking with dyno oil over syn and if and when the coking breaks loose and gets in your engine you will do far more damage than an oil leak or an oil with 1or 200 ppm of less zinc in it.
I have seen it. oil tube spray bar hole gets clogged and eats up a cam lobe and rocker.

Rayho · 12-27-2018, 06:48 AM

I drive maximum 1000 km each year. I don't think it will be a problem

Mocker · 12-27-2018, 07:24 AM

Agree with T77911S: Fix the problem, don't (mis)treat the symptoms!!!

full quack · 12-27-2018, 12:40 PM

Not wanting to give erroneous information, I did some follow up investigation on engine oil additives vs CATS. So yes in deed, some oil and fuel additives can cause premature CAT failure. The long 101 page oil thread over in 911 technical section is informative and has some good quantitative data, but for the most part relies on opinions, and only indirectly addresses issues with CATs. After all, it is an oil thread, not a CAT failure thread.

Silicon or Teflon use in either exhaust gasket/sealing or oil treatments, is a "major offender" in CAT failure. Predominately because these tend to out gas when burnt and coat the O2 sensor, which leads to incorrect fuel mapping in fuel injected engines, causing premature CAT failure.

MMP and lead in fuel are the #1 players in failures, but both have been removed from fuel a long time ago.

Zinc additives in oil can also play a roll, but it is considered a "very low level player", and as long as "extra" amounts of zinc additive are not added to the engines oil, a level of 250 ppm is considered not a "significant concern". Extended periods of high load use easily burns off any residue left from this 250 ppm level of additive.

However, 250 ppm level in commercial oil is a hard figure to quantify, as the oil companies do not state that specific information on their product containers. I searched high and low and could not find enough quantitative data to compile any sort of brand/type list that complies with 250 ppm.

Several "off road only" oils state they have zinc content or high zinc content. I could not easily find actual ppm values for any of these oils, nor do I really care, since none of them are intended for street engines or formulated to be used on CAT equipped cars anyway.

Anyway, that's what I found out surfing the ever reliable internet...…..?

Mark

speednme1 · 12-27-2018, 07:16 PM

Mark unfortunately how much zddp gets added in each bottle of oil is proprietary information that no manufacturer would share. I work for one of the few manufacturers and operate the chemical reactors that makes the additives...including zddp. We have a few grades of zddp(one grade more expensive than the other). Once we make it, it is sent off to different tankage to be blended off. Then picked up by tankers and off to their respective owners. I will say this, almost if not all motor oils contain zddp...what’s the ppm per quart? Your guess is as good as mine.

timc · 07:52 PM

Interesting quick read, apparently there may be some neg effect, but its a non issue as you don't have a cat...

I'd do my homework/fix problem, and maybe look at other synth oils before I'd go back to mineral....but it's your engine. FWIW, I've been using AMSOIL exclusively for the last 105K miles. No oil leaks, very rare that I smoke on startup, change it every 5K with analysis, or once a year.... 140K miles on the engine (never apart) and climbing and runs great.

https://www.amsoil.com/newsstand/classic-and-vintage/articles/reduced-zddp-and-wear-protection/