Originally Posted By: BrocLuno
OK, I'll buy that one, but how many BITOGers are running ships engines ... I never worked on a ships system where we were changing 1,000~5,000 gallons of lube oil where we did not do a lab analysis of the top-out if a gradual change.
And almost every time it was because of a system failure that contaminated the oil. The TBN was blown by the time we got to it. But, ships have to make maintenance ports where they have access to contracted work. So you do emergency repairs, top-in 500 gallons and off they go. They will get proper fixes and new oil as soon as possible. And they have a lab sheet that says what the issue was/is, and that the mix will work ...
That has nothing to do with a 5 qt car system, or even a 10 gallon truck system ...
See, that's part of the problem...yes, there's an example, but it has nothing to do with cars/trucks.
Same principals apply, largely the same additives for the same reasons, just more emphasis on certain aspects in certain formulations...
The advice "never have a problem", and "no-one has ever posted evidence" are clearly wrong.
http://papers.sae.org/2000-01-2942/
http://papers.sae.org/2000-01-2944/
http://papers.sae.org/932831/
Two car papers and a tractor.
Truth is that issues are rare (rare is infinitely more common than non existent).
Truth is that the majority of impacts are at the extreme cold end, where the "W" rating is most seriously affected, thus my initial comment that the worst is that two 0Ws aways equal a 0W.
Truth is that any negative interaction can be avoided for less the $10.
Moderate climate, moderate useage, and moderate oil changes, the end user will "likely" never see an issue (unless those unfortunate taxi operators (still trying to refind the paper) where the mix didn't allow the oil to pump even at freezing).
I'm not discounting your experience, by any means, but blanket "mix away" statements without qualifiers is IMO poor advice.
BTW, never gets below -8C here, and I mix....within the lines of the Pennzoil advice on the main page (stay within product lines), and advice from a guy involved in creating the product line that I use....
Quote:
It's an interesting one. Certainly no guarantee of 0W being achieved but without knowing the oils it's difficult. Often PPDs are universal across an additive suppliers range. But if you had two oils with different DI, PPD and VII you might cause problems with used oil. Even if Ccs is ok for 0W
MRV can also run into problems when certain VMs are combined with other PPDs.
In my own car I will only top up with oils using the same additive system. (Diff grade can be ok if I'm desperate ) but I want to ensure no issues. (Eg silicates and sulphonate detergents mixing are not ideal either)