Oil Weights and Numbers

Seeing the thread about a DE who seemed to have the wrong idea about
communication frequency areas on a chart made me think of something
that's been bugging me since my check ride.

The DE asked, "What kind of oil do you put in the airplane we're going
to fly?" I told him the plane used 50 weight ashless dispersant oil.
He replied that the plane actually used 100 weight oil. I was pretty
sure he was wrong but I let it go.

Later, I grabbed a pint out of the box in the office and it said "50W"
but also had a "100" above that. I see why he made the mistake. Or did
he? I dug around on the AeroShell web site and found products labeled
similary:

OIL W 100 SAE 50 - ASHLESS DISPERSANT

Looking through their FAQ, it appears that this a multi-viscosity oil.
Is that right? 50-100 multi-weight? Why is the label different from
automotive oil (e.g, "5W-30")?

What's really confusing is the W in front of the 100, followed by SAE.
Maybe there's an organization other than the SAE that sets the standards
for aviation oil?

-Scott

Scott Lowrey wrote:

Maybe there's an organization other than the SAE that sets the standards
for aviation oil?

You've got it. 100W aviation oil is 50W SAE.

George Patterson
If you don't tell lies, you never have to remember what you said.

"Scott Lowrey" wrote in message
news:xGEic.24898$IW1.1210282@attbi_s52...
[...]
Later, I grabbed a pint out of the box in the office and it said "50W"
but also had a "100" above that. I see why he made the mistake. Or did
he? I dug around on the AeroShell web site and found products labeled
similary:

OIL W 100 SAE 50 - ASHLESS DISPERSANT

Just to clarify beyond George's answer...

The oil you looked at was NOT multi-weight. It simply had both kinds of
units printed on the bottle. Like your soda bottle showing fluid ounces and
liters. It happens that the two measurements are exactly different by a
factor of 2, making conversion easy.

Pete

In article xGEic.24898$IW1.1210282@attbi_s52,
Scott Lowrey wrote:

The DE asked, "What kind of oil do you put in the airplane we're going
to fly?" I told him the plane used 50 weight ashless dispersant oil.
He replied that the plane actually used 100 weight oil. I was pretty
sure he was wrong but I let it go.

Shell has a lot of publications about aviation oil on their website.
Among other things their FAQ mentions that you can mix any of their
oils, so you don't have to know what's in the plane, you can put in
anything suitable.

--
Ben Jackson

http://www.ben.com/

"Ben Jackson" wrote in message
news:iM0jc.36507$w96.2637433@attbi_s54...
In article xGEic.24898$IW1.1210282@attbi_s52,

Shell has a lot of publications about aviation oil on their website.
Among other things their FAQ mentions that you can mix any of their
oils, so you don't have to know what's in the plane, you can put in
anything suitable.


That still didn't make me feel better when I put that quart of 60 weight oil
in with the 15W50 when it was 15F outside. Man, did THAT ever take a long
time to pour. In hindsight, maybe running a quart low for the 30 minute
flight would have been a better idea? Well, it was only 1 quart out of
10...

In article ,
Mike O'Malley wrote:

That still didn't make me feel better when I put that quart of 60 weight oil
in with the 15W50 when it was 15F outside. Man, did THAT ever take a long
time to pour. In hindsight, maybe running a quart low for the 30 minute
flight would have been a better idea? Well, it was only 1 quart out of
10...

Oil sumps are sized to allow maximum duration flights at maximum oil
burn without getting below the minimum quantity needed for safe operation.
The IO-540 requires some tiny amount (2.75qt sticks in my mind, but I
don't know if that includes the oil cooler and filter volume) but holds
up to 12qt. It will blow out most anything above about 10qt. The
Lycoming formula for maximum burn works out to be on the order of 1qt/hr.
So if you get 6-7 hours of endurance that would allow you to start at
10-12qt and end up in a safe (but low!) range.

So if your engine is one quart low, and it's not burning oil very fast,
you probably don't need to add any.

--
Ben Jackson

http://www.ben.com/