Viscosity Trends
by Ryan Stark Blackstone Labs
April of 2017 will mark my 20th year here at Blackstone and in that
time a lot of changes have taken place. I’m a big fan of change
myself. Long ago I got some advice from my Uncle Dan who said, “The
only thing that’s constant in life is change.” I decided that his
words were the truth, and it seems to me like change should be
embraced because there is no stopping it, and also for the most part
change is good. It might not seem good at the outset, but if you give
it some time, things eventually work out. After a bit of reflection on
the changes in the oil industry, I’ve decided that one of the best
ones has been the trend to lower viscosity oils.
The thin oil trend
I started changing my own oil on a regular basis in the early ’90s,
and at that time 10W/30 was the oil of choice in my 1981 Chevy
Citation. I didn’t think that much about it. It said right on the oil
cap use 10W/30, so I bought whatever was on sale and went along fat,
dumb, and happy. At that time 5W/30 oil was starting to be as common
as 10W/30 on the shelves, but I never went with it because it wasn’t
what GM said to use. However, my wife’s first car (1994 Buick Skylark)
recommended 5W/30, so that was a sign that thinner oils were starting
to come into favor. Again, I didn’t think much about it, and basically
just stuck with what was recommended when I changed her oil.
Then, in the early 2000s I noticed that we were starting to see a lot
of samples from Ford V-8 engines that were running 5W/20 oil. This was
a bit of a surprise since that’s pretty thin oil, but it was hard to
argue with the results. Those engines produced some of the best wear
we would see on a regular basis, so it quickly became obvious to me
that this was a change for the better. And if you think about it, it
makes sense.
Wear at start-up
For years, it was taken as fact by a lot of people that most of the
wear in an engine happens at start-up. Now I haven’t done any studies
myself to see if that was true, but that statement didn’t seem out of
line from what I know about engines. So assuming it’s true, why would
just starting an engine cause wear? Well, I believe the answer is the
oil isn’t flowing over all of the parts like it does shortly after
start-up. I do know that engines have virtually no metals parts
touching one another without a thin film of oil providing a
lubrication barrier, at least once oil pressure has been established.
I also know that thin oil pumps easier than thick oil, so it seems
obvious that the quicker you can get the oil to the parts, the less
wear an engine will produce. From then on I was sold on thin oil.
So what’s the problem here? Well, when I first started at Blackstone,
I was told that thick oil is good for the bearings, and I didn’t have
cause to doubt that statement until I saw these Ford V-8s producing
virtually no wear, and I knew some of them were work trucks that were
hauling heavy loads. So could it be that the bearings didn’t need
thick oil to survive? The answer is a resounding yes.
Even for diesels?
That trend toward thinner oil has proven true everywhere except for
diesel engines. For years and years and even today, the oil of choice
in a diesel has been 15W/40. But, if a heavy-duty gas engine can run
light oil, why can’t a diesel? We would occasionally see diesel
samples from Alaska that were running 5W/30 and they would look fine,
so why not use it down here in the lower 48? In colder weather, it was
acceptable for diesel to run thin oil, but that really only matters on
start-up. But the oil doesn’t get thicker as it heats up -- it thins
out. So could it be that thin oil does fine even when it get gets up
to operating temperature? The answer to me was another resounding yes,
and I wondered when the day would come that 15W/40 would no longer be
the manufacturer’s choice for diesel engines. Well, that time has
come!
Today we are starting to see more diesel fleets going to 10W/30, and
I’m here to tell you that this change is good. Not only will the
bearings do just fine, but the engines will start up better
(especially in the cold). And this change might eliminate the need for
plugging your diesel in at night. Now, there will always be some
people who are resistant to change. In fact there are whole countries
that are. The German vehicle manufacturers have yet to embrace thin
oil, though I think that change will happen some day.
Yes, change is good and I have yet to see a change happen that leaves
hundreds of thousands of vehicles stuck along the side of the road.
The sulfur has been virtually removed from diesel fuel and your old
tractor still runs fine.* Additive levels have been lowered in engine
oil and the old flat-tappet engines still run great. And now thinner
oils are here to stay. I’m excited to see what the changes the next 20
years might bring and I believe that I’ll embrace it, unless it
involves getting rid of oil altogether!
