I think we are in semi-agreement about the inaccuracy of determining
oil usage via repeated dip stick readings. I think it is far to
imprecise to yield repeatable results, but that is just my opinion.
I haven't owned a road vehicle since the 80's that used enough oil
between changes to cause a problem (and even then, it was only a
British vehicle that used a lot of oil). But If I develop a desire to
figure out precise oil consumption for a particualr vehicle I think
I'd do the following:
1. Find a dead level spot and park the car in an easily repeatable
position (heck I might even mark the tire locations). Let the car sit
overnight if possible. Record the vehicle's mileage.
2. Drain the oil completely (let it sit for at least an hour). Remove
the old filter.
3. Reinstall the drain plug
4. Weight the new filter, record the weight of the new filter, then
install the new filter.
5. Weight each bottle of new oil before pouring it into the engine.
Weight the bottle after the oil is poured into the engine. Substract
empty bottle weight from full bottle weight and record the weight of
oil added to the engine. Repeat for each bottle. Record the total
weight of oil added.
6. Start the engine and check for leaks.
7. Allow engine to cool and sit for an extended period of time. When
satisfied the oil has drained back to the oil pan, pull the dip stick
and scribe a line to indicate the "full" level.
8. Drive usual pattern and check the oil level at least weekly.
Monitor the change compared to the scribed line as a precaution. Don't
add any oil.
9. Plan to change the oil whenever the level dropped to the "add"
level or at the normal oil change interval (whichever occurs first).
10. When it was time to change the oil (based on step 9), park back in
the prior spot (step 1). Let the car set in that spot overnight if
possible. Record the vehicle's mileage.
11. Weigh oil catch pan.
12. Drain the oil into the pan. Let it drain for at least an hour.
13. Remove the filter carefully and try not to lose any oil (but have
the drain pan underneath to catch as much as possible should any
14. Pour as much oil as possible from the filter into the drain pan -
allow to drain for an extended period.
15. Weigh the pan of oil. Subtract the empty pan weight from the full
pan weigh and record the weight of oil.
16. Weigh the filter. Substract the origianal weight (step 4) from the
used filter weight. Assume this is mostly oil and add to the weight of
oil from step 15.
17. Have a sample of oil analysed.
18. Subtract out any moisture, antifreeze, solids, etc. listed in the
oil analysis report from the total weight of used oil (step 16).
17. Subtract the adjusted weight of used oil (step 18) from the weight
of new oil added (step 5). This is roughly equivalent to the oil
consumed over the period. Convert this to quarts (or whatever) and
divide by the mileagae interval (mileage recorded in step 1 minus the
mileage recorded in step 10).
This is about as accurate a method as I could come up with. Will I
ever do it? Probably not. It actually seems insanely complex for a
single person / single measurement, especially considering a precise
measurement of oil consumption for a particualr vehicle is of little
practical value. If I have a car that uses so much oil I need to be
concerned, I am going to get rid of it. I have farm tractors that use
1 or 2 quarts a day when working hard (but they hold 20 quarts). I
just add as necessary. The usage is completely unpredictable. For some
jobs the APPARENT oil consumption is negligible. For other it is
dramatic. Ususaly I check the oil once in the morning and again at
lunch time. Sometimes I have to add a quart both times, sometimes
neither. If the oil usage gets really bad, time for a rebuild. Really
bad in my opinion would be 2 quarts in 4 hours of hard use.
Repeated dipstick readings is like counting all the legs and tails in a
herd of cattle. It could get you the same result as counting heads, but
the chance of introducing error is significantly greater.
It sounds like it should be accurate , but you didn't have the scale
certified and you didn't check the air in the tires :)
I've driven oil burners in the past and you don't need to be
excessively anal to figure out the rate of consumption fairly close. I
drove a car that burned a quart every 600 miles for about 10 years. I
could predict within 20 miles when it would be at the ADD mark (checked
cold). The first quart after an oil change would go 800 miles but that
was mostly because filling it with 5 quarts brought it up to about 1/4
quart over the full mark.
Fifteen years ago you could get a 2-1/2 gallon container of oil for 6-7
bucks. That was enough to change the oil and keep it filled for about
3800 miles. Driving an oil burner today would be expensive.
On 6/10/2010 12:22 PM jim spake these words of bullshit:
Once again you put me in the unenviable position of agreeing with beam.
For that alone, you deserve to roast.
In point of fact, keeping track of the amount of oil you have added from
point a to point b, whether those points are distance or time, gives you
the total oil consumption for that period.
That doesn't change whether you check the dipstick level once or a 100
Grow up or shut up, kid. Or at least try thinking before you type.
"To argue with a person who has renounced the use of reason is like
administering medicine to the dead." -- Thomas Paine
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