"Joe" wrote in message
oups.com...
On Oct 28, 8:07 am, Bruce in Bangkok wrote:
On Sat, 27 Oct 2007 13:11:25 GMT, Brian Whatcott





wrote:
On Sat, 27 Oct 2007 13:08:19 +0700, Bruce in Bangkok
wrote:

I've only switched in the cars... no problems at all.
According to the local
mechanic, you can mix oil and synth without problems.
-
I've used one quart of Castrol synthetic to 3 quarts of Castrol
mutigrade changed each 4000 mile interval since new,
for over 300 k miles on two festivas, where the engines
work for a living.

Brian Whatcott Altus OK
-
-
Not to be picky, but why a mix of synthetic and multigrade?

Bruce-in-Bangkok

I once witnessed an extreme pressure oil bench-test.
Basically, a ball bearing is pressed hard onto a rotating shaft
and left to run. With mineral oil, there was soon a good flat.
With synthetic, the ball held in there, much longer.

But then, they cut the synth lubricant with mineral, and
the wear life held up at fair dilutions.

So, in view of the cost difference, and knowing they are
designed to be completely miscible, I used the 1:4 cut.

Finally, the makers started marketing a synth mix, but I do
it myself still - its no trouble to do. (The only precaution I take
is to use both types from the same maker - I chose Castrol)

I have read often enough, that synthetic can be searching in old
engines and unclog them or loosen seals and also that they
may not carry crap as well, and staying runny, the oil can
drain from cylinder walls
so it could be hard on startup, but the improved flow at
startup makes that point moot, I'm guessing.

Brian Whatcott Altus OK

Interesting. I had always assumed that synthetic oils were more
durable as they stood up to high temperature better but your test
seems to say that they have a higher lubricity factor.... Or perhaps
it is the resistance to heat. But, for whatever reason it seems that
they provide better lubrication.

So - why not 100% synthetic? Cost?

Bruce-in-Bangkok
(Note:displayed e-mail
address is a spam trap)- Hide quoted text -

- Show quoted text -

Someone explained to me that the synthetic mocules are all the same
size, like billions of BB's, where as regular oil would be like
billions and billions of BB's all very different sizes. So the load on
Synthetic could be carried easier and more even than regular oil. This
friend has a Cumming's Dodge truck and said he gained almost 10%
better mileage. He said once you switch do not go back or you will get
leak problems, but if you stick with it you will not have any
problems.

Joe



Well, now we've heard all the ways... leaks if you switch to synch, leaks if
you switch back to regular oil, not effective if you combine them. I've done
all three with older car engines with no problems.


--
"j" ganz @@
www.sailnow.com