Originally Posted By: Tom NJ
Like SonofJoe I am not a mechanic, and have not done any deep engine work in over 40 years. I also do not know the Redline formulations, but having sold them lots of polyol esters back when I was working I don't doubt their statement that their oils are rich in POEs, blended with PAO. And I know nothing about Hemis, but I was a synthetic oil formulator and do know a bit about esters, so I will try to shine a little light on POEs.
The most common POE used in motor oils is TMP C8C10 which has the following properties compared to PAOs:
Property............TMP C8C10.....PAO 4.....PAO 6
KV @ 100, cSt............4.35.........4.1........5.8
KV @ 40, cSt..............19...........19.........31
KV @ -40, cSt...........5,600.......2,900.....7,800
Viscosity Index..........140..........126........138
Pour Point, °F...........-65...........-87........-71
Flash Point, °F..........490...........428........475
Noack, wt%................3............13.........6.4
Density, g/ml..........0.943........0.820......0.827
Polyol esters can be thought of as PAOs with some oxygen in the molecular chain. Both are pure synthetic compounds consisting mostly of branched hydrocarbons, but the esters have multiple "ester groups" inserted, each containing two oxygens. These ester groups make the molecules polar, i.e. attracted to each other, which accounts for the dramatically higher flash points, lower Noacks, and higher density for a given viscosity. The polarity also imparts lubricity due to metal attraction, and better solvency. The solvency not only helps with solubilizing additives and allowing higher doses, but also dissolves and/or disperses breakdown products, thus reducing deposits at high temperatures. The combination of high and low temperature stability with cleanliness at high temperatures is why POEs are used exclusively in all jet engines worldwide. Even a small addition of PAO would cause the jet turbine oils to fail a specification.
While POEs are essential for jet engines, they tend to be overkill for car engines, and expensive. Some properties that do benefit car engines, however, are high lubricity, high solvency, and low volatility, which is why some synthetic oils continue to use them for PCMOs in spite of the cost. As SonofJoe has theorized, the high doses of POEs in Redline oils could in theory unstick lifters and improve lubrication, but whether this is a factor in the Hemi ticking is unknown. It would take a lot of very expensive testing to prove a correlation and it appears the problem is not frequent enough to justify the expense. If you have a ticking problem, however, an OCI of Redline is a fairly cheap way to see if it works for you.
Tom NJ
PS - Do not use jet engine oils in your car engine!
Tom,
A couple of questions if I may...
Why are POEs so expensive? My recollection (from VERY long ago!) is that they cost more than PAOs. If TMPC8C10 is the way to go, isn't everything ultimately derived from crude (as opposed to natural fatty acids) so should be cheap-ish? Also, although I'm a pretty rubbish chemist, isn't a simple esterification reaction super easy (and cheap) as compared to say decene polymerisation (for PAO), multi-step hydrocracking/paraffin isomerisation (for Group III's) or Fischer-Tropsch synthesis (for GTL)? I only ask the question because if Esters cost, say somewhere between Group III and PAO, I could easily imagine a route to getting them to be more mainstream.
I'm almost embarrassed to ask this (I'm supposed to be a Chemical Engineer!) but for a given viscosity grade and a given engine, do very dense Ester based oils give you higher oil pressure than say a low density Group II? If no-one's ever checked, it might be a worthwhile experiment.
I know PAO based oils usually contain 5 - 10% Ester to stop elastomer seals drying out but I'm now of the opinion that POE's are sort of wasted in this role. Has anyone seriously considered using POE in cheap Group II 5W30s as a simple Noack trim or as a counter to the very poor solvency of these oils. With the OEMs so fixated on LSPI and 0W8/0W16 this wouldn't be easy but I would have thought some kind of test development to demo the benefits might bear fruit.