Question on oil temperature
 

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

Anthing below 220F is fine IMHO.

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.

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.

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

Bob

= 248F lmao!

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.

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.

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.

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.

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.

My understanding of the process is a follows:
The PCV valve is the path to remove condensation (which is a product of combustion) from an engine as it gets warm, A cooling system temp of 185F to 195F (85C - 91c) is requires to vaporize moisture from the oil. Accumulated fuel in the oil is vaporized at a lower temperature. Under normal conditions, oil temperature is usually 15-25 degress hotter then the coolant temperature. Oil oxidizes at temperatures above 250F causing varnish deposits. The ideal temp for oil is 195F (91C) (Note: Water boils at 212F or 100C)

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----

Hmmmm, where to begin.

- The PCV valve is there to reduce smog. By products of combustion pass the rings (blow-by) and enter the crank case. The PCV system pulls them out of the crank case and re-introduces them to the combustion chamber to be re-burned. That reduces emissions, and also reduces power.

- Condensation is not a by product of combustion. It is caused by a rapid change in temperature, which takes the water out of solution and it precipitates out - condensing into the oil or other surfaces.

- Water vaporizes at anything above ambient temp and humidity. The higher it is, the faster it happens. If it had to be >185*, your kitchen floor would never be dry.

- Oil temp is usually higher than water temp. How much depends on a lot of facters. Oil is mostly heated by rpm's. If you're racing hard on the track, oil temps will often be 50-60* higher than coolant. If you're loping down the highway on a cold morning, oil temp is often below coolant temp.

- Oil oxidizes and forms varnish at any temp than it's designed operating temp. Cheap Circle K oil may do that at 250*. But a true synthetic will easily manage temps much higher than that. And don't forget that time is a huge facter. 300* for 5 minute is much easier on oil than 250* for 5 hours.

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

Really, enlighten me further vis a vi the water leak in my Buell XB12X please. Maybe in Carlsbad this doesn't happen, but here on the southeast coast this can happen anytime the temp drops and people don't operate their internal combustion engines to full operating temp on a regular basis. That means gas or diesel; water, oil or air cooled. The “brown muck” would be properly termed an emulsion, and while I would agree with others who’ve said that “evaporation” can occur at almost any time, when the water is suspended in an emulsion it is essentially trapped by enveloping oil thus slowing or nullifying any ambient temp evaporation. If, on the other hand, the engine and its fluids are brought to full operating temp (my Canton thermostat doesn’t open until 212 degrees F) then that same water becomes gaseous not just vaporous. At this point, what water is trapped in the emulsion will be released during the resultant expansion allowing it to be vented. The salient point is that if the oil is never brought up to sufficient temp for this to occur then the emulsions will continue to collect and hold water. If this emulsion reaches the sump and is pumped through the oil system then this will result in damage to the engine and I don’t see how anyone could argue that point as it is not an unknown occurrence. And just so that we are clear on this; water (gaseous) IS a major byproduct of the combustion process. For those who didn’t take chemistry in high school (or don’t remember it) gasoline would be represented by C8H18. Its combustion, in the easiest sense of the word is to carbon dioxide and water and could be expressed thusly: 2C8H18 + 25O2 ~> 16CO2 + 18H2O

Absolutely correct, combustion creates water vapor. In a perfectly performing combustion engine, the hydrocarbons react with Oxygen and turn to water (vapor) and CO2. The Nitrogen would simply pass straight on through into the exhaust. This is why emissions controls have been able to reduced the CO2 output, thus resulting in a cleaner burning engine.

And if anyone needs further proof of this, come look at my wife's car....it gets driven about 1.5 miles in the morning, then parked all day and 1.5 miles home and parked all night...in the winter, by the time she gets to work, the heater is just starting to blow warm air..take off the oil fill cap and you'll see just what Steve is talking about..“brown muck”. I try to use it for my work (about 250 miles per day of highway driving) at least once a month to help minimize this....
and if that's not enough, come by my shop and I'll crank up my race car for you and you can see for yourself. Each valve cover has a 12AN fitting with a 3/4 inch inside diameter clear hose going to a vented catch can in the passenger front corner of the radiator support, so the clear lines are about 3 feet long each.When I crank it up when the outsdie air temp is say,60 or lower, the condesate in those clear hoses is amazing, I'd bet a tablespoon in each during warmup, that's why I have them going down hill so the condensate will flow into the catch can and not back into the engine. but the point is, the block and all internal components are cold and condensate will form on the inside of the crankcase/block and drip down into the oil pan...long drives at highway speeds gives this time to vaporize or evaporate off......on the race car, a 20 to 30 minute race with my oil temp at anywhere from 220 to 250 degrees will take car of the condensate, that and frequent oil changes......
David