Switching and mixing oils- additive 'conflicts'?

[Simplysimple]

I recently read (unsure of the accuracy, though) that when switching from one oil to another, the new set of additives may 'wash away' the beneficial deposits left by the previous oil's additives, leaving the metal surfaces with a reduced level of protection until the new additives leave their deposits. Is there any truth to this?
Also, is there any reason not to mix certain oils, based on their additives, and any possible conflict between the two different sets of additives? I just started mixing 2 qts. 'old' Pennzoil Platinum, with 3 qts. MaxLife synthetic. This is just a practical move for me, since I have lots of oil (580+ qts.), and want to use at least a little MaxLife in my higher-mileage car ('95 Caprice Classic).

 

[daytrader106]

You post a great thread.

When we converted our FL-70 to full synthetic in the rear end. I was told THAT SHOULD NOT BE DONE and will void your warantee.

I was told there is DINO fluids in the rearend from the factory and the synthetic would cause a severe gumming problem. Asked how to do this they said I had to break down the rear end, the axles and do a chemical clean to ensure NO dino fluid remained. We did this and added full synthetic oil. NO PROBLEMS.

I wander if all this was needed.

 

[Pablo]

Boundary layers can change, the old removed boundary layer material ending up in the current oil....but in reality this does not leave metal contact surface "with a reduced level of protection" to the extent of reduced engine life, excessive wear, etc. It is common with an oil such as Redline to see some UOA elevated metals the first change or two, but this is probably more from the cleaning of old oil deposits. I tell you, it's not a thing to worry about. People here change oil brands/types more often than I change my shorts and they have pretty clean engines - which will last until they hit a pole.

Mixing oils..........not necessarily for the amateur, but sometimes people hit on winners. Other times, nothing exciting.

 

[Simplysimple]

Originally Posted By: Pablo
It is common with an oil such as Redline to see some used oil analysis elevated metals the first change or two, but this is probably more from the cleaning of old oil deposits.

Mixing oils..........not necessarily for the amateur, but sometimes people hit on winners. Other times, nothing exciting.


Thank you.
Yes, I'm not worried about measurable adverse affects of switching oils. I'm just nitpicking, hoping for the absolute best I can do with my oil, and also to know the effects of my actions. You mention elevated metals in a used oil analysis after a switch probably coming from old oil deposits. Are you saying that oil deposits have wear metal in them?
"Mixing oils.. not necessarily for the amateur". That implies possible adverse effect. Do you mean adverse effect caused by additive pack 'conflicts', or by some other reason? I'm just speculating that those conflicts even exist, of course.
I have a bunch of oil, but not enough MaxLife to last for as long as I'd like, if I use exclusively that, without mixing it with some other oil.

 

[ekpolk]

daytrader:

As Pablo suggested, we've had more instances of soup mixing here than I can remember, and I can't recall any reports of an actual problem.

I have read that back in the early 70s (IIRC) in the dawn of synthetics for automobiles, there were some poorly developed di-ester based synthetics that would actually form a rubbery goop if mixed with mineral-based products. I would not be surprised if that was the source of the report you heard (but of course, that's just my "informed inference" and I might be wrong...).

 

[daytrader106]

As the New MX modle STILL has dino in the rear ends. This should be published. I do not feel there is much concern as MANY of these have been drained and replaced with the norm run of syn fluids.

The FL-70 MOST times the shop has no idea that it is dino fluid not the NORMAL syn type.

I wanted to cover my rear and did what I was told. Our MX came with FULL DINO NOTHING syn. In most trucks noe this is not normal. Most have syn rear end and transmission fluid.

Just the being told that this will void thing got me. UNLESS YOU do this and this. Maybe a Myth Busters lead? I do feel lubricants have come a long way. Out with the old and in with the new.

Its funny how the same guy that will ONLY use so and so brand oil in his car will JUMP on the new heart med isn't it?

 

[Steve S]

Most all the additives are the same in all the oils .I wouldnt worry about it.