the big spikes in iron (caused by rust) that I
had always seen when the aircraft was idle
for a month or more were eliminated. That
got my attention. I also found a modest
across-the-board reduction in other wear
metals (about 10 to 20 percent). I examined
the oil analysis history of several other airplanes using CamGuard and saw much the
same thing. I’ve been using CamGuard in my
engines for more than three years now, and
I’m convinced the stuff works.
For most of the airplanes we manage, we
recommend AeroShell W100 with a pint of
CamGuard added at each oil change. That’s
what I use in my airplane, and my two
engines are at nearly 200 percent of time
between overhauls (TBO) and still going
strong. For wintertime operations in cold
climates, I recommend Phillips X/C 20W- 50
multigrade with a pint of CamGuard.
OIL CONSUMPTION
Take any group of aircraft owners and it’s
not long before they’re comparing notes on
MI/HR on Oil
MI/HR on Unit
Sample Date
Make Up Oil Added
44
2,608
08/02/10
4 qts.
UNIT /
LOCATION
AVERAGES
33
2,564
05/02/10
3 qts.
ELEMENTS IN PARTS PER MILLION
ALUMINUM
CHROMIUM
IRON
COPPER
LEAD
TIN
MOLYBDENUM
NICKEL
MANGANESE
SILVER
TITANIUM
POTASSIUM
BORON
SILICON
SODIUM
CALCIUM
MAGNESIUM
PHOSPHORUS
ZINC
BARIUM
5
10
46
4
6113
2
3
27
1
0
1
0
0
5
1
75
2
58
1
0
7
8
38
3
5840
1
3
16
1
0
0
0
0
5
1
20
1
46
2
0
5
11
44
5
4778
0
3
35
1
0
1
0
0
5
0
59
1
65
0
0
whose airspeed is the highest and whose
oil consumption is the lowest. I’m here
to tell you that low oil consumption is
highly overrated.
Lots of factors affect oil consumption.
Six-cylinder engines use more oil than
four-cylinder engines. Big-displacement
engines use more oil than smaller-displacement engines. Chrome-plated
cylinders use more oil than steel cylinders.
Nickel-carbide cylinders use less oil than
steel. And so on.
Anything from a quart in 20 hours to a
quart in four hours is normal. I’ve seen
engines that burned a quart in four hours
throughout their entire life and made it
past TBO without any problem. I’ve also
seen engines that used hardly any oil and
then wound up needing a top overhaul after
500 hours.
TCM doesn’t consider oil consumption
to be a cause for concern until it exceeds a
quart in three hours, and says that it isn’t an
airworthiness issue until it exceeds about a
44
2,531
12/28/09
4 qts.
7
13
52
5
5238
0
3
27
1
0
1
1
1
6
0
11
1
6
1
0
50
2,485
06/28/09
6 qts.
8
12
58
7
5049
2
4
25
1
0
1
1
1
7
5
48
2
36
3
0
50
2,435
04/05/09
4 qts.
7
12
47
4
6515
2
4
34
1
0
1
2
0
5
1
67
2
68
3
0
55
2,385
08/25/08
4 qts.
7
8
45
4
6122
3
4
21
1
0
1
0
1
6
0
63
1
46
2
0
UNIVERSAL
AVERAGES
8
8
40
4
5511
1
3
14
1
0
0
0
0
6
1
15
1
214
3
0
quart per hour. I don’t think any of us would
allow our horizontally opposed engines to
get to the point of burning a quart per hour,
simply because it’s embarrassing to run out
of oil before you run out of fuel.
I get concerned about any sudden
increase in oil consumption. If an engine
has been using a quart in 12 hours for most
of its life and suddenly starts using a quart
in six hours, something has changed and
that’s a red flag. Until we figure out what
changed, we can’t be sure whether it’s serious or benign.
I also get concerned if the oil starts to
turn black and opaque quickly after an oil
change—say, within 10 hours or so. That
indicates excessive blowby, and some testing
and troubleshooting is needed to determine
why this is happening and which cylinder is
the culprit.
Many owners install aftermarket air-oil
separators to reduce oil consumption and
keep the belly clean. I don’t like air-oil separators because they return all sorts of ugly,
Here is an excerpt of an oil analysis report from Blackstone
Laboratories in Fort Wayne, Indiana, on the right engine of my
Cessna 310. (I fly a twin, so I get two reports at each oil change.)
The report for my left engine was unremarkable.
The column on the left is the most recent sample, taken on
August 2, 2010. The engine was then at 2,608 hours since major
overhaul (more than 1,200 hours beyond TCM’s recommended
TBO of 1,400 hours). Aluminum, chromium, and iron all look
great—those would be from pistons, rings, and cylinder barrels,
respectively. Copper is fine as well—that would be from bearings or thrust washers. Lead is low, indicating that the engine
does not have excessive blowby. Silicon is also low, so the air
filter is doing its job nicely.
The one red flag on this report is nickel, which is more
than twice what it has been historically. The only source of
nickel in my engines is exhaust valve guides, so there must
be a valve guide that is experiencing accelerated wear. The
elevated nickel has been present for at least two years, but is
gradually increasing. Sooner or later, there will be a burned
exhaust valve in my future.
I did a compression test and borescoped all the cylinders,
so I know that none of the exhaust valves are leaking or showing any abnormal heat signatures…yet. But the oil analysis is
telling me that an exhaust valve problem is inevitable, so I’ll be
watching closely. Of course, the oil analysis can’t tell me which
cylinder is having the problem, but that’s something I’ll know
in time by means of continued borescope inspections and
keeping a close eye on my digital engine monitor. Eventually,
a distressed exhaust valve will become evident, and the corresponding cylinder will need to come off for repair.
