I finally got the '74 2.0L running well and went for a 20-to-30-minute drive. Temps were in the upper 80s and I'm not sure if the car was getting to hot.
Since there are no digits on the gage, I need to ask. I found a drawing of gages, so I think I'm in the 240 area. Not sure if the temp was still going to rise since I was back at home. The photo is from the passenger seat but from driver side, the "P" was mostly covered by the needle.
Am I still in the safe area? Thanks for any knowledge on this.

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You need to confirm what temp sending unit is in your car before you can infer anything from the graphics.

200C sender was original but 50 years later, unfortunately, lots of temp senders have been swapped for the 150C aftermarket senders which changes the gauge calibration.

150c or 200c is stamped into the sender.

However, 240F oil temp (worst case - 200c sender calibration) is not dangerous though it does seem high for the 20-30 minutes of driving you described.

You might want to pickup an IR temp sensor to double check.

How is she running?

I changed all the center console gauges to new VDO gauges and senders. Changed the clock for an oil pressure gauge. 240 oil temp is getting hot, higher oil temps effect oil pressure. What weight oil are you using?

So I gonna stir the pot on this. What is a good average temperature? I have seen many different people say different things. Mine runs at hottest 190-200 but I am depending on a gauge and sender that has variable range of accuracy like everyone else. I saw post the other day from Charles Navarro stating that all air cooled engines should see 220 sustained in order to burn out moisture from the oil. A friend runs 240 on his 914-6 and he is a constant state of freaking out. I would think 250 should be max but now question that based on accuracy of the gauge is it really that hot?

Charles is correct.

250 is not dangerously hot by any stretch. Even less so with modern synthetics.

Most of your modern water pumper daily drivers will be well over 205+ at sustained 70-80 mph highway speed. All air cooled motorcycles run way over 200F oil temps.

Air cooled engines are not water pumpers. They run hotter and so does the oil.

Constant source of amusement for me how people believe internet mythology and what daddy or grandpa told them based on early 20th century machinery. It doesn’t help that the Bruce Anderson book pushed the 180F mythology.

Oil temps run much hotter than they did back in the “good ol’ days of V8s everywhere when most engines were due for a rebuild in less than 100k miles. Yet . . . Today, no one is surprised when a modern engine goes 200k miles running hotter oil temps.

Let me stir the pot a little more

Porsche set the red “danger” redline at 300F. Do folks think VW & Porsche didn’t know what they were doing based off durability and dyno testing? And remember that redline was set in the days of conventional Dino oil. Not saying anyone should run at 300F continuously but even 300F isn’t a big deal for synthetic. 300F is a very reasonable redline.

make sure that the bellows flaps are installed and fully open and there is nothing restricting the air flow into the fan, and that the lower heater plumbing is installed

I'd want cylinder head temp as well.

To me, CHT is more important than oil temp.

300 peak is fine for synthetics.

300 continuous would bug me

Above 250 continuous on dino would be the same.

Now, a track only car I'd hunt for lowest temps possible at all times.
Oil dilution would not be an issue with 5–10-hour oil change intervals.

Anything street based (long oil change interval) I'd WANT to see above 212 during every drive to reduce the moisture.

Lest anyone accuse me of just propagating my own mythology here is an excerpt from an engineering text on air cooled engine. Note: this book was first published in 1961 and second edition in 1972 . . . So again Dino oil era.

120C =248F
80C = 176F

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If anyone is interested in this book here is a link to 1st edition of an otherwise expensive book.
https://archive.org/details/air-cooled-moto...-.m.-e/mode/1up


Correction to my previous post
The Bruce Anderson book doesn’t reference 180F as max temp - my mistake

It is confusing and contradictory though. At best he’s saying 200F oil but then goes on to say 220 is high end of proper operating temp. I think people latched on to the lower number thing less is better (not true). I clearly latched onto that same lower number in my memory.
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As long as it is NOT in the red, nothing to worry about. Keep it simple.

I have the factory temp gauge and a capillary tube temp gauge on my /4.

I like 210 to 230

However ... If that is your oil temp, I would be curious about your head temp.

And I agree with the don't fear the hot oil. Fear the hot head though.

OK. lots of great info. I do personally like the "If it's not in the red" simple answer. Looks like I need to research a little on what I have on the car. I really don't want to dig into the sender risking oil leaks I'm trying to reduce currently.
One comment mentioned the flaps which I know, I need to check to see if they're open. And the heater plumbing is there. CHT sensor I believe is now disconnected sine I switched over to carbs. And the guy that switched the carbs also changed the oil so don't recall what he said he put in.
Superhawk showing the book makes me feel more comfortable, that a normal, high temp would be 248 and, if my sender matches the gage, I'm under the high mark.
I need to go for another, longer, drive and test more. It's been hot in my area and no A/C in the 914 with me getting a little older. Gotta wait a few days.
BTW - "How's it run" = I posted her in the past on getting the FI to work right. 3 shops and I couldn't do it so went to carbs, now runs very well. Seems the FI had snappier throttle response, but the carbs make it "drivable".
Thanks for all the responese and great info.

the thing about running at an ideal temp of 90C is pretty true.
both my water pumpers run at a consistent 90C (top of the dial - mid way).
renault clio RS and and audi A3.

but they are water pumpers.

the old air cooleds do waver around a bit and find it harder to precisely sit at some constant temp. but ideally it should be around the 90-100C range.

i'll just add thats why i was always taught to change the oil in my old VW at twice the recommended intervals. engine temp is one. oil condition another.
of course modern oils are so much better as @Superhawk996 says.

or of course there is always the smell test.
you can smell a hot motor.
its a distinct odour. trust your nose.
if all else fails.

The fi cht is not useful for engine monitoring. You want something like a Dakota digital. It's a little ring you put around plug #3 and gives you a realtime view of cylinder head temperature.

I find my cylinder head temps need to be quite high for a while before my oil temps go over 210 but every car is different.

When restoring my '73 2.0 several years ago I sent the oil temp gauge to N Hollywood Speedo and they added actual numbers with a new sensor. Nice to see actual temps on the gauge.

Hopefully they sent you a sender that is calibrated with the markings on the temp gauge. If not, the numbers are guesswork.

I like 212F for oil temps. That's the temp that the "normal" viscosity tests are done at, and it's one that makes sure that any water in the oil will boil out relatively quickly. At 180F the water will still outgas, but it will take longer.

IIRC, the Anderson book for aircooled 911s calls 230F "hot", 240F "too hot", and 250F "too damned hot". I'm pretty sure he was referring to non-synthetic oils, though. I wouldn't panic if a synthetic oil ran 250F for a while because they are a lot more tolerant of thermal abuse. I would, however, try to figure out why it was so hot and try to do something about it.

--DD

Good thread and of interest to me.

Another data point. My 2258 runs oil temps in the 230 to 240 range if I'm in stop and go traffic on a 85+ degree day. Once I get some motion and air movement under the car the rear mounted air cooler will drop it back to 210 to 220. I find lower (ish) RPM's and highway speeds cool the oil fastest. People worry about head temps at lower RPM's but mine rarely go above 300. The combustion chambers were coated when Len Hoffman did the head work.

I probably need to stop stressing about the oil temps.

Yeah, I like my low oil temps cause I hope they can keep the heads cooler. 250 isnt anything for a good modern synthetic, however, if it's 250 at the sump it's hitting far higher temps in the tight spots, which, again, is fine for a good synthetic, but eventually....

I wish I had some Lenny heads.