Originally Posted By: Patman
Originally Posted By: addyguy
IF synthetics aren't 'slipperyer' than 'regular' oil, the WHY are they always used in applications calling for max fuel economy?
I'm not sure, but let's put it another way. If synthetic oils truly were more "slippery", wouldn't we see significantly lower engine wear in the used oil analysis posted on here? But after more than ten years on this site I have not seen that to be the case at all, many of the best used oil analysis on here have been with conventional oils.
That's because conventional oils often leave considerable deposits. Those deposits, when tested contain large quantities of wear metals.
Aircraft engine manufacturers require mineral oil for break in. Interestingly enough, aircraft engines with oil consumption problems (poorly broken in rings) will often be "fixed" by a 50 hour run on mineral oils.
I know it's a different world, with air cooled engines, and huge tolerances. But, there is some validity to wear rates and oil type. Interestingly, aircraft engines show very little metals in used oil analysis. Yet, wear is rapid. But a test of the gunk deposited throughout the engine reveals where the metals go.