What should the "OEL" gauge read?
 

What does this gauge represent and what should it normally read?

Which one?
There are 2 gauges, one for pressure and one for level.
Technically, there are 3 because the temperature is also oil related.

There's also a third oil gauge for temperature, at least in an 87, not sure about a 75.

It should correspond to the oil level dipstick - both of which can only be read accurately when the engine is up to operating temp ~177F, idling (around 850rpm) and on level ground.

The other 2 oil gauges are the Druck (pressure) which should read roughly 1 Bar (~14.7psi) per 1,000rpm when warm and the Oil Temp gauge which is self explanatory and should read between 177F and 210F when driven (180F is optimal). If your temp gauge has no numbers, it's best if the gauge never exceeds about half-way (the Red zone is very harmful and you should never approach it).

Here is a link with info on each gauge for ya... http://forums.pelicanparts.com/porsche-911-technical-forum/395607-oil-related-gauges.html?highlight=oel

The needle on the gauge will change significantly during operation. As GrantG said, it should only be considered to give a true indication when the engine is idling and @ 176 degrees; with the car on a level ground. It should correspond to the level on the dipstick, and should be approximately half way between the 2 marks to be considered "full".

Thanks for the insight into the oil gauges. I had the ole girl out yesterday on one of the few beautiful sunny days we have had in chicago. I am a new owner of an older porsche and i did not know what the OEL gauge was. Gosh...I looked at the gauges as i driving, and the needle was buried in the red. So I used my pda to write this post on Pelican and then received a response within minutes that gave me the answer I needed so that i could continue on my beautiful drive. I checked my oil level yesterday using the oel level gauge and the dip stick and I am right where I need to be.

Thanks all for the education on the fly!

Greg
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75 US Carrera
03 Cab 2
69 Z11 Camaro Pace Car