Hey all -
The question of change intervals and synthetic oil has come up. As a side
at work we run oil tests using the Shell Four Ball test rig. This tester
was developed by Shell oil to test the extreme wear properties of motor oils
- cams, piston skirts etc. It consists of three, = inch balls held in a
triangular pattern in a cup with oil heated to 165 degrees. A forth ball is
lowered to the center of the three balls and loaded to 40 KG. The ball is
then rotated 600 RPM for one hour. After the test the wear scar is measured
on the three stationary balls. The bigger the scar the lower the extreme
wear property of the oil is. We use Havoline 30 wt for a base line. We use
this oil because engineers from the past liked this oil, so we have a large
data base.
Looking at data shows new Havoline 30 wt has a wear scar of .0165 inches.
New Mobil 1 has a .0145 inch scar. May not seem like a lot of difference,
but it is. Havoline 30 at 3000 miles has a wear scar of .020 inches and
Mobil 1 at 4000 miles has a .0164 scar. Remember - the bigger the badder.
3000 miles is as long as anyone was willing to run Havoline 30 wt, so its
data stops here. Mobil 1 at 6000 miles is .0167, at 8000 miles is .0188,
and at 10,000 miles is .0194. So, at 10,000 miles Mobil 1 has better
lubrication properties in the critical areas in your motor then a good 30
wt. All mineral oils follow Havoline pretty close - major brands. Some off
brands have a .020 wear scar new. Multi-grades generally have a larger wear
scar as well. This data was from a 5.0 Ford Mustang. Every motor will be
slightly different, but not much.
So, synthetic can handle long run intervals. But, that is part of the
story. You have contaminates to deal with. This is where the additive
package comes in play. This is the expensive part of oils and the reason
synthetics are high priced. Because of the long run intervals of synthetic,
they must have a vastly superior additive package - and they do. Proof of
this is to take 3000 mile dino oil and look at it in a glass jar - then do
the same for Mobil 1. The Mobil 1 will look new compared to the dino oil.
I run Mobil 1 in my new cars to the longest manufactures oil change interval
- usually 7000 miles. This will keep the warranty happy. In my Roadster I
change it once a year regardless of mileage. It run my Roadster about 5000
miles a year. Most people at work run synthetics and do the same. We have
a bunch of cars in the lot that have over 200,000 miles on them and going
strong. I (my wife) never keeps one that long.
I run 10w-30 Mobil 1 in my new Roadster motors (after break-in). Older
motors get 15w-50 because the tolerances are larger. Because synthetics
don't thin down like mineral oils do at temperature, I would be careful
running 15w-50 in a motor with a high volume oil pump. By doing so you may
run into cavitation problems - oil gage jumping wildly. Drag racers
experience this often at high RPM. Drop a wt and it will clear up.
I checked the auto parts stores last night and could not find a zero wt
Mobil 1. It was about 2 years ago they were talking introducing this oil,
so apparently they have in some markets. I stand corrected.
Testing another "magic" oil additive today. It looks and smells like
linseed oil! This should be fun. Additives are another subject all
together. Another day, but never tested a good one - none- zip - zero -
don't waste your money.
Sorry for being soo long. I like synthetics (obviously). If you have been
to the conferences, seen all the tests and data, and read the lubrication
journals you would run nothing other then synthetics.
Phil
SEROC
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