A recent post regarding excess exhaust smoke due to overfilling during an oil change got me thinking ... I had a similar overfill issue and I filled to the Porsche specs listed in the owners manual after doing all the proper draining.

How much oil are you guys putting in during oil changes -- slightly less than prescribed by Porsche? Any input much appreciated

 

On any car I put in about .5 quart less than it calls for, then run for a while, then re-measure to top off.

On the p-car I run it just above the half way mark as the "top off mark".

Also fill the plastic filter housing part way before you install it.

After I recently R&R the heads on my 1999 car, it took 10.5 quarts to get it to the "top off mark".

A typical oil change though with less draining time might take ~ 9.5 ish quarts.

 

+1 for run it at the 1/2 way mark as "full"

unless you like oily exhaust tips

 

I usually put in 8 quarts not including the oil I put in the filter housing, start it up and let it run for a few minutes (i check for leaks at this point), then turn it off and let it sit, then I check the level and bring it to just above the midway point between max and min.

 

9 quarts in a drain and fill with filter replacement, using a spin-on filter, not stock.

9.5 quarts if the pan is removed and drained for an extended period.

Either one put it 1/2 way on the dip stick and 1/2 way on the guage.

 

The oil change instructions (from the factory manual and reinforced by the techs I talk to) instruct one to bring the engine up to temp (80C) then raise the car and drain the oil for 20 minutes.

Button up the engine then add a specific amount of oil. The amount varies from model to model, engine type to engine type. For my 03 Turbo the amount is 7.8l or 8.25 quarts. Now the Turbo oil level check is done with the engine up to temp and the engine running so I make another count of the number of quarts of oil I have put into the engine then start the engine and then drive it off the ramps letting the engine idle while I clean the tools.

When the engine is hot enough I do an oil level check and the manual says the lower 7 segments of the oil level display should be lit. For my car this means the oil level should be at the max line.

(I can add that even though I do not drain the oil with the car level and that 20 minute drain time is done without the benefit of a high precision timer there doesn't seem to be any problem with the amount of oil that is drained from the engine.)

What this does is it gives one the chance to verify the oil level display system (mainly the oil level sensor) is working properly.

In the case of my Boxster which has a dipstick I use this technique to verify the dipstick is reporting the correct level of oil and then confirm the in-dash oil level display shows the correct level of oil.

I asked some techs about the failure modes of the oil level sender and only one had encountered a bad one and he told me it gave no reading at all.

Also, I took an oil level sensor apart and it does not have any ability to report how overfilled the engine is. The purpose of the sensor is to report the oil level *only* after the person performing the oil change has added the specified amount of oil. The oil level sensor/sender can of course follow the oil level down but it has no ability to follow the oil level up if one insists on overfilling the engine. If the oil level reads over the max line one can't know if the engine has 0.25 quarts too much oil or 2.5 quarts of too much oil. The sensor/sender and oil level display are not intended to accurately convey just how badly botched an oil change/refill operation that ends up with the engine having too much oil dumped into it.

To put it another way, the primary means of determining the engine has the right amount of oil in it is to rely upon the amount of oil that was added to the engine after doing a drain as I described above. One counts the number of empty quart bottles of oil -- the techs dial up the amount of oil from the fluid dispenser in the service bay area -- and then using the known amount of oil in the engine one then verifies the dipstick and the oil level sensor/sender and the oil level display are delivering the expected reading.

Sincerely,

Macster.

 

When I drain my oil I drain it into a measured 5-gallon paint bucket. It's cut down so that it fits beneath a slightly raised 911. Cut down a standard 5-gallon paint bucket (like one of those orange things from Home Depot). Scribe it on the inside every couple of quarts. When you drain your oil, you will know precisely how much came out. Try to put back what you took out. Of course, there will be some captured within the oil filter, but not enough to matter.