Tegger's real-world oil consumption

This was also posted to www.bobistheoilguy.com ,
but accidentally to the "Diesel" forum. I've asked the moderators to move
it to the "Gasoline" forum.

My 1991 Acura Integra has (currently) about 343,600 miles on it. At this
mileage, it's sort of inevitable that oil usage is going to be a lot higher
than it was when the engine had fewer miles on it.

After a scare four years ago (the last time I posted in BITOG), I decided
to make a near-science of monitoring my oil consumption, so I could find
out how much oil I was REALLY using.

The results of two-years of testing have led me to several conclusions:
1) ambient air temperatures make no difference in consumption, but age of
oil might;
2) usage cycles up-and-down regularly, for no apparent reason;
3) it takes a long time and many test-cycles to determine a trend.

The chart is here:
<http://www.tegger.com/hondafaq/misc/graph-may28-10.pdf>

I did this chart for "summer" only, which covers from about mid-April to
late-November, outside of which dates the winter tires go on, and mess up
the method on account of their slightly larger diameter.

I've tried to be as consistent and as accurate as possible with my testing
methods, but I think 17 cycles covering approximately 35,000 miles and 24
months is enough to detect the engine's actual consumption.

Hope this is of interest to some here.

 

It's of interest to me; over this time frame, you averaged about 1660
miles per quart of oil. That's not bad, given the wear on your engine.
A lot of work, and good information. And something the rest of us can
measure oil consumption against.

I wish there were more folks doing this level of information-gathering.

Thanks, Tegger.


RFT!!!
Dave Kelsen

 

I think the above represents a well-done study.

I too would think that oil consumption would be pretty consistent over
the 41k miles. But taking into account errors in measurement,
consumption perhaps is pretty consistent. For example, using the chart
linked above, the reader can surmise that the average consumption was
about 1660 miles per quart (mpq) with a range from 1500 to 1850 mpq,
or +/- about 10%. Reading error for each measurement taken would maybe
be around 0.04 quart ( = about one-half a gradation = about one-half
mm on the calibration chart next to which you held the dipstick).
Temperature effects might cause an error in reading of around +/- 0.03
quart (= .0005 per degree F * 20 degree F * 3 quarts). You monitored
every 1k miles or so, so I gather you did two readings of the dipstick
per data point. Each reading could be off by 0.07 quart. Hence any
given data point might be off by around 2*(.04+.03) quart = 0.14 quart
or around 10% error, consistent with what your readings were. Hence I
would say the variation you found might be explained by the
measurement error involved in doing readings. Hence the average number
you found is useful.

I see from the "Bob is the Oil Guy" (BITOG) thread you used Mobil 1, a
synthetic oil, for the entire study. I think this may be relevant for
some readers. E.g. those who are still using non-synthetic oil might
expect higher oil consumption for an engine the same age as your
Acura's.

(Anyone wanting to see Tegger's thread at BITOG should just do a BITOG
keyword search for "Tegger.")

 

I'm a bit surprised that nobody in BITOG has brought up this extremely
important point. I was fully expecting to be called-out on reading
errors, but nobody's done that yet except you.

As you point out, the obvious uncontrolled variable here is my dipstick-
level-recording method: It's a simple visual comparison between dipstick
and chart, which is subject to some guesswork as to the exact position
of the "meniscus".

Of course, the level doesn't go in increments that match the markings on
my chart, but is usually in between the marks. Is it closer to one mark
than the other? Do I call it 6.3? 6.4? It takes very little change in
what I record to make a big difference in the final mileage number.
That's part of the reason I need very many records in the dataset; it's
the only way of materially reducing the inevitable contamination caused
by reading errors.

I take at least four readings each time I do my readings, just to be
certain I'm reading the level correctly. Even then there is some
"fudge", since the oil runs down the stick fairly quickly, especially in
warmer weather. I need to make sure I check the level quickly, before
the level at the "meniscus" thins-out so far that I have difficulty
locating the top of the "meniscus".

I had been using M1 for some time before my decision to keep precise
records, and kept using it just to eliminate a variable.

I have, though, also discovered that M1, over more than 100,000 miles,
produces FAR less varnish than Castrol GTX did over the same mileage.
I've been sufficiently impressed with M1 that I wish to keep using it.

 

You're welcome. The testing continues apace. An update will be issued at
some point in the future, once more records are generated.

 

I don't know why you're changing oil every 3K. Any reputable oil such
as Castrol, Valvoline etc should be good for at least 5K.

JT

 

[politically incorrect humour follows]

What kind of lap times do you think Helen Keller could achieve on the
BBC TV show 'Top Gear'?

 

Hi, I am not sure what you mean by "called-out," but I want to be
clear that I was not trying to criticize your work. Rather I was
curious about the variation and whether it might be explained by
measurement error. I think the variation is not meaningful and is to
be expected. Your study is /extremely/ well done. I doubt any other
DIY-er could get a narrower range for measured oil consumption. Your
study is instructive in a few ways, in fact.

I guess I might also keep in mind that generally, oil consumption is
going to rise. As you know. So one cannot take an average of too long
a time period and have it be meaningful. Rather something like the
average over every 50k miles seems like it would be helpful to folks
as a measure perhaps of how much wear the engine is seeing.

Do you mind if I post a link to your chart and a summary of it at
honda-tech.com ?

snip for brevity

Yes, I understand: Lots of data points help average out any
measurement error.

 

(M.A. Stewart) wrote in

They once actually did have a blind man in their "reasonably priced car".
He'd lost his sight in a bomb-blast in some Third World country when he was
with the British military.

Jeremy Clarkson and he did /many/ test laps during which (with "Jezza" as
passenger) they'd worked out a rally-type system with Jeremy as navigator.

The blind guy did not finish last.

 

By "called-out", I meant I expected somebody to bring up the issue of
measurement accuracy when reading off the dipstick. The entire work
depends on that, of course. And nobody but you brought it up. That
doesn't say much for BITOG, frankly.

I'm complimenting you, is ultimately what I meant.

That is very possible. I considered the possibility myself, but had no
real way of compensating for it outside of large sample size.

I'm no statistician, but I've done enough testing and offhand
statistical analysis--both personally and as part of my job--to realize
that variability is the norm in statistics, and can be very difficult to
both account for, and to correct for, when attempting to determine
trends and tendencies within the numbers.

I'm not totally sure what accounts for the variation. As you point out,
it may well have to do simply with the vagaries of my vision and with my
judgments as to the exact fractional positioning of a particular
reading.

I found that if I considered a reading as being 0.1 of a mark higher or
lower, that made as much as 500 miles per quart difference in the final
analysis. I had no way of correcting for that other than sample size.
When calculating gas mileage, one faces the very same variability
problem.

My reading-records were conservative, normally erring on the side of
higher consumption. IOW, if I wasn't quite sure, I'd guess on the higher
side (6.4 usage versus 6.3, etc.).

If what I'm seeing is accurate, I believe consumption rises very slowly
over the years. I believe that the reason some people see a sudden large
hike in usage is because they never check their oil. And then one day
they do, and it's a LOT lower than they expected. They conclude from
this that it all-of-a-sudden started happening.

Please do. When posting to BITOG, I was hoping for somebody to chime in
with meaningful technical criticism and advice. So far, you're the only
one. Maybe we can get others in hondatech.

Hey, you're doing peer-review! Cool!

Lots of data points = large sample size.

 

dude, with the greatest of respect, and don't take my pedantry
personally, but there are a number of things here which are really bad
practice and a correspondingly bad example for other users.

1. you're dipping the oil too long after shutdown. you should be
following the procedure honda specify - "a couple of minutes after
shutting the engine off". it is the only consistent method available to
all users, all conditions. you are an adherent of the owners manual
after all...

2. your change intervals for the oil you're using is way too short. i
can see a shorter interval if you're trying to de-gum an engine that's
been abused, but here, you're wasting both money and resources. if you
want to spend the money on something useful, spend it on analysis, not
wasting oil.

3. don't over-think this meniscus thing. all you need to do is ensure
consistency. if you're serious about making quantitative measurements
[as opposed to monitoring trends - the real objective here], install a
sight tube and vernier. and make sure you take thermal expansion into
account. see #2.

4. again re #2., you should allow for batch differences in the base
oils. mobil /do/ use a proportion of group III in their base, and that
proportion varies from batch to batch. it stands to reason that the
gIII's greater propensity to breakdown will give you variance in
consumption levels in line with content proportions. what you should do
is stick to a longer interval and you'll find that the aggregate total
over the full cycle is more consistent. the rate of consumption drops
as the volatiles burn off, so this will have a better averaging effect
that is more consistent with your vehicle's consumption over the use
cycle, not reflecting the oil's composition and initial burn-off rates.
[you can also try mobil's eco or extended performance blends - a lower
proportion of gIII's and in my experience, lower oil consumption.]

 

indeed. he's using mobil 1 - he should be looking at 10k at least.

 

oops, forgot to mention:

among other reasons, oil temperature and whether or not the oil filter's
anti-drain-back valve is functioning are factors here. dipping at full
working temperature is consistent. dipping before drain-back happens is
consistent. anything else is subject to considerable variance.

 

I'm sure he beat Al.

 

Checking your oil every day before the engine is started is consistent,
and tells you how much oil you have in your system. As Tegger pointed
out, you want to do it while the car is in the same physical location as
well, to eliminate vagaries of level.


RFT!!!
Dave Kelsen

 

consistently wrong. for the reasons stated above, it needs to be
checked after the engine has attained full working temperature and has
been shut down for "a couple of minutes". like when you've pumped gas.
all gas forecourts are level. just dip the oil when you fill up.
like it says in the honda manual.

no, dipping when cold doesn't. it doesn't allow for temperature
differences, and it doesn't allow for filter drain - i.e. whether or not
the anti drain-back valve is functioning. filters are very inconsistent
in that - tegger should know - he's written about it before.

again, the only consistent and accurate method is to dip as above.
after all, it's where the dip stick marks are positioned to be read -
there is always a difference between hot and cold, and honda are
positioned to be read hot.

 

I have only seen a few of the shows. But I do remember briefly seeing
on the tower of lap times, close to the bottom (and above a few others...
poor folks), the pasted-on 'Blind Man' lap times. I didn't believe it at
first... but later I saw it again, and thought it was a riot (a politically
incorrect riot of course). I had assumed that they had possibly
blindfolded a person to get the lap times.

So do you think Helen Keller could turn better lap times than the 'poor
folks' below the Blind Man (hypothetically)? What about Patty Duke?
Could she turn better lap times?

 

Your whole PDF is almost too utterly ridiculous to even comment.

Your explanation of your methodology is rather confused. You claim to
take measurements every 1000 miles which doesn't jive with the mileage
numbers shown on the chart. You cover period of 41000 miles. That
should mean (if you took a reading every 1000 miles) 42 measurements,
but your chart only shows the result of 17 measurements. So what about
the other 25 measurements that should be there but you don't show?
The 17 points on the chart don't show data they show some dubious
calculation you made from whatever data might have been. The data itself
is probably also dubious. You may have a mark on your dipstick when the
sump is full and a mark when the oil is down a quart, but that doesn't
mean that half way between those 2 marks is where it is where it is at
half a quart low. This would be due to the irregular shape of the oil
pan.

Using your method is like using the gas gauge to calculate gas
mileage. With that type of bogus measuring someone might conclude: Gee
for some reason I always get 40 mpg on from full to half a tank and
then get 20 mpg on the second half of the tank.
All you have really proved is that with the first reading of the
dipstick you get some reading plus or minus one notch on the scale. And
with the second reading you get plus or minus some other notch on the
scale. You consistently get to around some point on the dipstick at 1000
miles and consistently get to around some other point at 2000 miles. And
that is about all you can say conclusively.


Here is what it looks like to me.

1) At 3000 miles you change the oil.

2) After 1000 miles you infer from your flawed measuring system that it
has used about .65 quarts at that point which means it went 1540
miles/qt. In reality the engine has really only used .5 quarts at that
point in the cycle which means it has really gone 2000 mi./qt.

3) At 2000 miles you check the oil and infer from your measurements that
it has used .55 quarts which means in that interval it has gone 1800
miles/qt. But in reality it has used .7 quarts on this part of the
cycle, which means it has actually used 1430mi/qt. in this interval. At
this point the engine has used a little over a quart on the dipstick and
so you add a fresh quart.

4) At 3000 miles your chart indicates you don't do any
measuring/recording data you just change the oil and repeat the
foolishness from step 1).

The fact that you repeat the same bogus methodology over and over and
get somewhat the same results repeatedly - you interpret as being
meaningful.

That appears to be obvious. You're Not much good at accurately
collecting or reporting meaningful data either.

-jim

 

The chart says near the bottom: "Not all 1,000 mile intervals were
recorded (some were missed for various reasons)." This happens in
experiments all the time. When it does, the question is: Are there
still enough sample points for statistical meaning? IMO, yes.

Tegger stated at the BITOG site that after "the first level check I
top it back up. Then I top it back up after the second check. At each
check-time it's down a bit more than a pint, depending."

Hence before he adds oil each time, he must be reading near the same
point on the dipstick each time. He might be a little off, but given
he knows how much he adds to bring the level to full, I doubt he is
far off. Given how often oil checking is discussed here, it would not
surprise me if he checked for linearity on his Integra's dipstick.
Some dipsticks apparently are pretty linear from low to full. Not all,
but some. At any rate, give him a chance to answer.

Someone at honda-tech.com suggested he instead measure how much oil is
needed to bring the level back to the full mark. Presumably he is
adding oil very carefully to top off the level, and so the volume
could be measured.

 

That doesn't even begin to answer my question. Why is most of the data
missing? Why isn't there any data for how much was used between 2000
and 3000 miles? If there was any serious attempt at accuracy, there
could have been an accurate accounting of the total consumption for the
entire oil change interval plus an accurate accounting of how much was
added along the way. This doesn't even begin to look like a credible
study.

Well that is a rather important detail to suddenly introduce after the
methodology has been questioned.
So what is all this nonsense about measuring ticks on the dipstick? Why
not accurately measure the amount added to get it back to the known full
level?

If he does know that actual amount added to get it back to full, why
would the calculations be made from the dipstick readings? It makes no
sense at all.

I'm a little suspicious of anyone who leaves out the most important
details and then when the deficiency is noted they suddenly come up with
a story. If they understood the importance from the beginning then why
would they have not mentioned it from the beginning.
The most important detail that is excluded is why does this study look
like it is just cherry picked data. I can see no good excuse why all the
data was not included. Nor is there any reason to believe that the 40%
of the data that was given is representative of what all the data would
have shown if it had been collected and reported using credible
methodology.