Checking your oil level on your 911 (65-89) and 914-6

By Tom Gould

A common question I get from new owners of older 911’s is how to check the oil level. 

They are confused by the oil level gauge on the dash (the oil level gauge is in the same instrument face as the fuel gauge – 914-6 and some early 911’s don’t have this gauge), and by the fact the engine has to be running to check the level on the dipstick. 

A couple of things that should help:

1.   There should be a decal on the rear engine compartment sheet metal that has the oil level checking instructions,

2.   The owner’s manual also explains how to check it.

Guidelines for checking your oil level:

The engine has to be warm (about 170-180F) and running at idle to get an accurate reading.

Never try to check the oil level with the engine cold or not running!

Always trust the dipstick reading over the oil level gauge reading.

Never overfill the oil tank!

Ignore the oil level gauge while you are driving. It is common for it to read empty, full, or bounce around in between while you are driving around. This is normal and not indicative of what the correct oil level is. 

The only time you should be reading the gauge is when the engine is warm and has been idling for at least 30 seconds.

Here’s the way to check your oil:

Warm the engine up until the oil temperature gauge just gets up to the 180 degree mark (80 if your gauge reads in Centigrade), or until it just gets up to the first white line (about 8 o’clock) on those gauges that don’t have a numerical reading. It will generally take at least 5-10 miles of driving to get the engine warmed up to that temperature.

Park the car on level ground, put the parking brake on, and let the engine idle.

Open the engine compartment and remove the oil cap (remember that things are spinning and things are hot!).  (If you have a 72, the oil tank dipstick is accessed through the flap in the right rear fender, not the engine compartment).

Pull out the dipstick and wipe it clean. Insert the dipstick back in the filler neck (there is a little tube it goes into), and then pull it back out and look at the oil level on the dipstick.  If it is between the two marks, then your oil level is fine.  If it is at the lower level or below, you can safely add a quart, and then recheck the level. You want the level to read somewhere near the middle of the two marks. The difference between the 2 marks is 1.5 – 2 quarts, depending on the year of car. 

Don’t over fill the oil tank! Excessive oil in the tank could cause rough running and a smoking exhaust.

As you check your oil on the dipstick, look at your oil level gauge and see what it is reading.  Make a mental note of what the oil level gauge reads compared to the level on the dipstick. 

Over time you can get a good idea what the oil level gauge is actually telling you.  Remember that the dipstick is always correct, so if you get a funny gauge reading check the dipstick for the correct level.

Make sure you put the dipstick back in the tube and put the oil cap back on!

If you don’t have a dipstick, make sure you get the correct one for your tank. 

There are 5 different dipsticks for the 65-89 911’s: 65-71, 72, 73, 74-80, 81-89.  The 914-6 uses a different dipstick, too.  Finally, the 73-80 911’s use the later (81-89) dipstick if the oil level sending unit in the oil tank has been replaced.

If you have any questions, you can reach Tom at TCsGarage.com 760-295-3330 or e-mail tom@tcsgarage.com