First of all, thanks for all the inputs...
So, the Rotella "syn" 5/40 is a SEMI-synthetic..
is the "synthetic" part more or less than some HM oils? say, for ex., Pennzoil HM 10/30 or 40?
[I remember reading here that Pennz. HM oils have "quite a bit of" synthetics in them]
Which of these would lean more towards synthetic?(I guess it's Rot. 5w/40...??)
What I'm trying to achieve is:
A) good cold-cranking performance ( a little syn), and
B)a 40-weight(i like thick oils for summer,
C)WITHOUT the typical seal-seepage/leakege-inducing levels of synthetic oil. (have a rear main seal-leak, running ARx with Chev. dino right now)
..all this with a OTC semi-syn or HM oil ppossible? probably not, but I want to try to find one...
and how about the Pennz. syn-blend 15w-40? anybody know how this oil is?
(Application: 3500-4000 OCI, 1997 4.6L sohc T-Bird with 88,000 miles, mixed highway/city driving, area: east TN)