Generically, the difference between pre-mix and concentrate is convenience: with concentrate, you do your own mix-down, and you have to source your own DI water (I use distilled, because I stock it for other purposes, and it's readily available, but if you like DeIonized water, it can be had).
Personally, I buy and use concentrate, but pre-mix is more convenient (at a slight increase in cost). One thing you can't
do with pre-mix is adjust concentration richer, which is something I used to frequently need to do when I flushed cooling systems, because all the old coolant (or flush water) does not leave the cooling system. With repeated fill/run/flush cycles, I could obtain a clear waste stream, but not a completely dry system. In that situation, being able to use a 40/60 (or whatever) water/coolant mix could get the overall system back to approximately 50/50.
The reason for 50/50? Less concentrate throws off the additive mix, and a weak mix can also raise the freezing point (and lower the boiling point), two of the goals of coolant in ICEs. Too much concentrate decreases pumping efficiency and heat transfer (among other things).
Tony Williams has stated
that coolant test strips that test the pH of the coolant can be used to determine coolant suitability, but I do not agree; that test methodology is valid for ICEs because they have specific coolant degradation patterns, which include accelerated pH decrease, primarily due to extensive dissimilar metals, thermal cycling well above what we have in our systems, and most importantly: pH decrease due to combustion gases leakage into the cooling system, which moves the pH down into the acidic range very effectively (same issue with pH in ICE lubricating oils, BTW, and the reason behind testing used engine oil for residual alkalinity . . . but I digress; Google "oil TBN" for more info.).
EV coolant isn't subject to the same stresses as ICE coolant, and test procedures should be different too. Personally, the stuff is cheap, and if the dealer doesn't gouge too much, I don't sweat it. I got my last coolant changes "free" due to warranty DU replacement @ 60k and warranty battery replacement @ 93k. I just turned over 106k, and I'm nowhere near 5 years since the battery change, so I'm OK for a while yet, and I've cheated and obtained a (hacked) Tesla Powertrain Diagnostic setup, so I can let it open the various valves and run the pumps while I change the coolant myself. It wasn't cheap, and is probably not worth the expense & hassle for most people, who just want to drive their car.
I can't let this one slide . . .
jimbo69ny wrote: ↑Wed Feb 13, 2019 3:09 am
Neither one is going to corrode. You don’t have to bargain hunt but you can be an aware consumer. These two fluids are one molecule different
. One is safe to drink the other is not. The only difference. They both do the same exact job.
One molecule different doesn't seem like much to you? Water (H2
0) and hydrogen peroxide (H2
) have pretty different characteristics, too
Arguing that "only one molecule different" makes something essentially equivalent for any particular use is groundless.