lube
Not knowing the exact product number put i do know that the mfg/blender of my eng lube (which isnt texaco) is The supplier and package'er for one of Texaco's high end transmission lubes,
Have not talked the the gentlmen that is the nat'l acct's director lately , a few years back tex signed up with them for superior lube supply (pat'/formular) being i use what is called a specilailty lube that is'nt sold over the counter and i have axcessto it from a passed life i have never got it under the star label.
Being he lives a few miles from me ill try to give him a call this week end ,He supplied me with the SAE spec' booklet years ago of lube break down on each letter -wt break down which i 'm sure is out dated (pre 92).
Under the old spec's 50 oil was 90 wt gear luge(diff additive package) ATF was 10 wt oil. . 15 w 30 is 15 wt oil with the lube quilatys of 40 wt ---- IN a Nut shell...
Tighter clearance's need thinner lube's which reduce weight and increese mpg's thru less eng drag. .
Take an eng with a 180 thermostat-- 60 psi oil press,raise the temp to 200-205 --regulate the oil press down to say 30-35
and mpg will rise.