newsboy

I was wondering if there is any discernible difference in the oil level gauge/dipstick, when the thermostat is in the open and closed positions?
My feeling would be that the oil lines to the front cooler would be full, whether the stat was open or closed, and that the oil level would not be effected. Am I right?

dfinnegan

Correct.

However, the discernible difference is in the temperature of the oil. Oil expands when hot. If you try to measure the oil level before the t'stat is open you will get an artificially low reading. In fact, having the temp above the 8 o'clock position is preferred, or, at the very least, up to the highest temperature you expect to see. For example, bumper to bumper traffic on a hot day. That way you won't ever heat up the oil to the point where it expands so far as to overfill the reservoir.

newsboy

The reason that I asked this question, is because in my winter driving, the thermostat often does not open. So the oil level guage/dipstick, (when I get back to the garage) and look at the guage, it looks 1/2-3/4 ouart low. (down near the bottom of the guage). I would not have thought that the temperature of the oil, would produce this much of a difference?

boxsey911

If you want to check the oil on a very cold day I would do it after you've given it a damn good thrashing for 30 minutes. That way you'll get a good warm reading and not be tempted to put that bit extra in. When I drive to the track with a correctly filled engine, the dash gauge reads half way on arrival. After 20 minutes of hard track work the needle gets close to the top of the gauge which illustrates the point Dave makes above about the oil expansion.

newsboy

Understood, Thanks.

dfinnegan

Half gauge reading, up to the top, would be a ~1/2 qt change.

breale01

Well, here's my story....oil change in July and gauge reads just a needle width below half way (good enough for me).

The colder it gets outside, the lower the gauge goes after a drive.

I just went for a 1 hour drive on the highway (70 mph) with a couple of hard accels down the on-ramps. Back at the garage, idling on level ground, the gauge reads low (at the white/red junction). Ambient temp during the drive was just a degree or two below freezing.

Dipstick check shows level at about 3/4 inch above lower notch.

The car doesn't leak (I know, a rarity) and doesn't burn oil.

Colder outside temps causing this?

Richard Curtis

Could be. As a comparison, I have an aftermarket temp gauge on my Merkur XR4ti. I drove it this morning (30 minute commute) at 70 mph with ambient around 40 degrees F. The temp gauge never rose above 150 degrees F (normally runs at 180-192), so engines do run cooler in cooler ambient temps. Although I haven't observed as much of a difference in my 964, it definitely runs cooler and takes longer for the gauge needle to rise above the 2nd mark (when the thermostat opens) during these colder days.