> 10w30 recommended for warm weather and 5w30 is not?
> It seems to me that they
> should be the same as far as heat is concerned. Do I
> have it backwards?
No, you have it correct Rob. By the way, I'm not D^2,
but I play one on TV. Actually, I'm R^2 <--little
star wars humor. very little.
As far as your question goes, when the weather is warm
enough, the viscosity of 10W is the best mix of "thin
enough to distribute quickly" and "thick enough to
lubricate well". Think of this: would you run WD-40
in an engine if it were really hot, even if its
"hot-run" viscosity were still 30? 5W is sometimes
used if its really cold, to offset the "molasses in
january" syndrome.
I've poured straight 30W oil in sub-freezing temps.
It is really like molasses.
I wouldn't use 5W anything in anything except a new
vehicle with tight engine clearances. the thinner
cold viscosity will not provide adequate lubrication
for an older engine with worn bearings and such. Even
if its synthetic. D^2 and I both use Mobil 1 15W-50,
though when I get my rebuilt engine back, I'll be
breaking it in with 10W-30 conventional. Afterwards,
I'll go back to the Mobil 1, but I might use 10W-30
since the bearings will be new. (even a brand new 440
doesn't have the tight tolerances a, say, Hunda VTEC 4
pumper does- that would use a 5W or even 0W oil.)
=====
--Mike Pittinaro
"Peculiar travel suggestions are dancing lessons from God."
--Kurt Vonnegut, "Cat's Cradle"
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