Question on oil temperature

[mattpatt]

Just thought I'd check with your experience on this. I just recently got my new Cobra on the road. It has an aluminum small block 351W 427. I noticed that the oil temperature generally runs 10 - 15 degrees C above the water temperature. Sometimes gets up arounf 105C (in ~80 degree weather). I have an 180 degree F thermostat. Does this seem normal to you guys?

What temperature should I worry about?

thx

Matt

[madmaxx]

Anthing below 220F is fine IMHO.

[Jerry Clayton]

oil temp needs to be ABOVE boiling temp of water(212*f, 100*c) in order to get the condensation out off the crankcase----

[Gaz64]

Originally Posted by Jerry Clayton

oil temp needs to be ABOVE boiling temp of water(212*f, 100*c) in order to get the condensation out off the crankcase----

Agree.

Optimum temp is around 120c.

[AL427SBF]

Originally Posted by Gaz64

Agree.

Optimum temp is around 120c.

= 248F lmao!

[jhv48]

If that is anything but freeway driving in 80 degree weather, then you're fine.

If that is freeway driving, then it's high.

Our remote oil coolers don't work worth a crap below 50mph.

[bobcowan]

Originally Posted by Jerry Clayton

oil temp needs to be ABOVE boiling temp of water(212*f, 100*c) in order to get the condensation out off the crankcase----

Common misconception, and certainly not true.

Oil temps generally runs about the same as water temp, plus a few degrees. Max temps depends on the oil in question, and time. 5 minutes at 250* isn't as big of a concern as 5 hours at 230*.

Oil is heated mostly by rpm's. 105*C (221*F) is a bit high for routine driving. That's something I would investigate. The first question would be - of course - is the dash gauge accurate? Once the oil is good and hot, hit the oil pan with an infrared thermometer. Not perfectly accurate, but should be fairly close.

If it's pretty close, then you have to wonder if your water temp gauge is accurate. Do the same thing, and check the thermostat housing. Again, not perfectly accurate, but should be pretty close.

Oil pressure that's too high will generate heat - either from a high pressure pump, tight bearings, or too much viscosity.

Viscosity is a big issue, IMO. Some people think that because the engine is in a Cobra, they need 20W-50 racing oil to go to cruise night. That's just not needed, and causes a host of other problems.

[lovehamr]

Originally Posted by bobcowan

Common misconception, and certainly not true.

It most certainly is true. I've experienced it myself with both cars and bikes. Have you ever opened an oil cap and found a milky substance on the underside? There you go, that isn't just oil and I don't live in an area that gets all that cold these days. When I lived in Delaware it was even worse.

[mpanten]

Originally Posted by lovehamr

It most certainly is true. I've experienced it myself with both cars and bikes. Have you ever opened an oil cap and found a milky substance on the underside? There you go, that isn't just oil and I don't live in an area that gets all that cold these days. When I lived in Delaware it was even worse.

Not true, if that were the case water would almost never evaporate. Ever make a cup of tea, it will steam well before it boils. The minimum you need is about 65C or 150. Natually warmer than that is better but you certainly dont need it over 212. Jerry is correct that the oil will be hotter than it actually reads on the gauge but if your oil temp is reading 120C on your gauge you have a problem.

[jhv48]

Normally you will get a lot of good info from this forum.

Not so much this time. Brown muck in the oil is generally caused by a faulty gasket or cracked block.
(water leaking into the oil) And 120 degrees Celsius is NOT optimum oil temp.

Your oil temp is fine. If it drops to around 90 at freeway speeds on that 80 degree day then you are golden. By the way, your oil temp is measured at the remote oil filter prior to it flowing through the oil cooler.

You're fine, enjoy the ride.

[Bob In Ct]

Probably depends on where it's being measured - crankcase, after cooler, prior to entering cooler.

Bob

[vector1]

been my experience that oil temp (also depends on where taken) is usually 20-30 degrees f above water temp. on a recent drive i watched the water temp increase and the oil go with it, also what i would expect. max oil temp depends on what the oil is rated for.

[Jerry Clayton]

OK----I stand corrected--there probably would never be any condensation of water vapor as the only place it could come from would be a by product of combustion---and all the cars are electric now???

If your crankcase isn't properly vented and somewhere the oil reach boiling point of h20, you will get milkyness mucccc in you crankcase----then down the road, bearing problems, rusty cylinder walls ,etc--

Its your choice-----try mixing water and oil and then lubercationg something--oh, thats right, water and oil don't mix!!!!!!!

The oil will probably be aprox 50* hotter on the bottom of the pistons and especially on those engines that we spray the piston bottomside to cool it.(common in many hiper/race engines these days)

The temperature you read on your guage will of course be the temp of the oil at that location in your system and not necessarily the temp at its highest value.

[Jerry Clayton]

I guess I'll just go back to trying to get that other 2 horse power so I can say I built a 500 in moter that made 1400 horse power at over 10,000 rpm----

[Jerry Clayton]

isn't true synthetic sorta like tight slacks????

actually the pcv caused a worsening of smog---it converted oil drips on the road to burning the oil and causing worse tail pipe emissions

[YerDugliness]

I've been wondering about condensate contamination recently on my (I think) box-stock 5.0 HO engine in my Cobra. I notice that on cool days the coolant temperature stays around 160* unless I turn off the puller fan on the radiator (it is a large Griffin radiator....at least it never overheats). If that is so, then the oil temperature must be even lower, as I seldom drive it anywhere near the upper RPM limits in town.

I'm just curious...what temp thermostats does everyone use? I have no idea what mine is, but think I'll swap it out for a 195* unit for the winter, then back to a 180* unit for the summer.

I guess I need an oil temp gauge more than I need the non-functional amp gauge (I have no oil cooler). Would it be best to connect the oil temperature gauge at the rear of the block, right in front of the firewall?

TIA for whatever advice y'all might have. I've seen engines all sludged up inside from failure to run a thermostat, but never gave much thought to the fact that failure to boil off the condensate in the oil might do the same thing.

Cheers!

Dugly

[DAVID GAGNARD]

Originally Posted by YerDugliness

I've been wondering about condensate contamination recently on my (I think) box-stock 5.0 HO engine in my Cobra. I notice that on cool days the coolant temperature stays around 160* unless I turn off the puller fan on the radiator (it is a large Griffin radiator....at least it never overheats). If that is so, then the oil temperature must be even lower, as I seldom drive it anywhere near the upper RPM limits in town.

I'm just curious...what temp thermostats does everyone use? I have no idea what mine is, but think I'll swap it out for a 195* unit for the winter, then back to a 180* unit for the summer.

I guess I need an oil temp gauge more than I need the non-functional amp gauge (I have no oil cooler). Would it be best to connect the oil temperature gauge at the rear of the block, right in front of the firewall?

TIA for whatever advice y'all might have. I've seen engines all sludged up inside from failure to run a thermostat, but never gave much thought to the fact that failure to boil off the condensate in the oil might do the same thing.

Cheers!

Dugly

I'm not 100% sure, but I think the 5.0 HO engines came with 190 or 195 degree thermostats. Depending if it's still EFI or carbed,(I see your engine is carbed, so 180 degree thermostat would be correct for it) I would use that or a 180 thermostat, nothing lower. Soounds like you have a very efficeint cooling system on your car, you might try blocking off a few inches of the bottom of your radiator with the wide clear packing tape to help keep the water temp in the 180 to 190 range...
I use the same 180 degree thermostat on my street car and race car!!!!!

Water temp has little to no bearing on your oil temp.,oil temp is determined by rpms and bearing clearance mostly and oil viscosity to some degree....not sure I understand what you mean by putting your oil temp gauge at the rear of the block, it needs to be low in the oil pan where it will stay submerged in oil to get any kind of accurate reading...
Idealy,to me anyway, water temp should stay bewteen 180 and 190, and oil temp from 190 to 220....

David

[YerDugliness]

Originally Posted by DAVID GAGNARD

I'm not 100% sure, but I think the 5.0 HO engines came with 190 or 195 degree thermostats. Depending if it's still EFI or carbed,(I see your engine is carbed, so 180 degree thermostat would be correct for it) I would use that or a 180 thermostat, nothing lower.

....not sure I understand what you mean by putting your oil temp gauge at the rear of the block, it needs to be low in the oil pan where it will stay submerged in oil to get any kind of accurate reading...

Idealy,to me anyway, water temp should stay bewteen 180 and 190, and oil temp from 190 to 220....

David

Thanks, David, for the advice...I'll definitely change out the thermostat while I have the valve covers off for gasket replacement!

As for my comment regarding the "oil temp gauge at the rear of the block", I guess the keyboard gremlins got me that time. I was trying to say "..sensor location for the oil temp gauge"...the rear of the block seemed to be the best idea as I thought there was a place to tap into the oiling system for a pressure gauge...I see now that those "ports" are coolant and vacuum "ports". I do have a Fox body oil pan on the Cobra right now, and there is a plugged port on the driver's side of the pan, directly to the side of the rear oil pan drain plug, that was probably for a factory "low oil" sensor, I'll try to use that location.

I am guilty of thinking that I need heavy viscosity oil in my pan...think I will switch to 15W-30 or 15W-40. Right now there is a very slight leak at the rear corner of the passenger's side valve cover, so I check the oil level every time I get in my car. It must be a very slight leak, I guess, as the oil level never seems to drop on the dipstick. My oil pressure VERY seldom drops to 40PSI, and usually at any RPM level above idle is at 60PSI (VDO gauges, no idea how accurate they are).

Cheers, and thanks, again! An oil temp gauge is definitely in my Cobra's future.

Dugly

[bobcowan]

- Water will evaporate from an emulsion at low temps - like 100*; it just takes a long time. Frequent short trips cause the sludge to develop because it gets warm for a very short period of time. Longer trips get the oil and water to higher temps, and for longer periods, that's why the sludge usually resolves. The end result is correct, but the cause- effect assumption is slightly off.

If you could run the engine for an hour at 100*, the same thing would happen. But, why would you do that? That would be a bad thing to do for a lot of reasons.

- A good spot for the oil temp sender depends on your engine set up. With an external cooler, I like to know what the temp is as it's going in to the engine. With no external components, the side of the pan is a good spot. With the proper adapter, you can put it where the factory level sensor used to be.

- A stock Mustang usually has a 195* thermostat. The higher operating temp improves emissions. The computer is programmed to look for that temp before switching to closed loop, and then it gets off the cold enrichment map. You can use a 160* or 180* thermostat if you reprogram the computer to see that as normal operating temp. Of course, if you've dumped the computer altogether and gone with a carb, you can use anything you want, and adjust the choke accordingly.

Lots of studies on cold weather operation show increased cylinder wall wear at temps <160* or so.

The thermostat only sets rough minimum temps.

- Water is a small by product of combustion. Because of the heat involved, you know the water is well vaporized. But, the condensation in every other part of the engine is not the same thing. On a good engine, the blow by will be 10% or less. If you're getting that much water simply from blow by, you have other issues to address.

- oil sludge is more of a problem in some engines than it is in others; the 2001-2004 Dodge Dakota 4.7l comes to mind. It was a problem even for people who made frequent long drives - 20 to 40 mile commutes. So, obviously engine design has a something to do with it. That engine even had a recall (or maybe a TSB?) on that particular concern. IIRC, the fix was something simple like a new PVC hose routing.

[jhv48]

Apples to oranges once again.

Engines are designed to be operated within a certain temperature range. If you fail to meet that requirement, condensation will occur and will not be boiled off. Duh! That's why manufacturers recommend more frequent oil changes for low mileage vehicles.

But, i am talking about normally operated vehicles. Ones that reach normal operating temps. If you notice brown muck in the oil of one of these vehicles, then you probably have a serious water leak.