Acceptable Engine Temps

[JIMOCO]

On the other forum there is a thread about engine oil too hot. I cannot post a new thread on that forum because I do not have a posting history. Hopefully some of the same people will be reading this as well. Reading that thread some noted that engine oil that is too cold can be as damaging to the engine as being too hot. My oil temp runs low (347 stroker, 650 cfm carb, 10:1 compression, street/performance cam). The gauge reads below 140 degrees during normal street driving. At idle on a hot day it will creep up to about 160 with engine temp at 180 to 190. Oil temp goes right back down once moving. I contacted speed hut (gauge manufacturer) and they sent me a new sender. Same result. Laser temp tool gives about the same readings at the oil pan (7 quart canton). I tested the gauge and at 1 ohm resistance it reads 200 degrees. This agrees with speed hut's specs. Engine builder says I should be happy with a cool running engine but the guys on the other forum are warning that too cool is not good. I have read that oil temp will run about 20 degrees higher than coolant temp. Oil pressure and all other gauge readings are normal. What are your thoughts?

[slaga]

I also have a 347/10ish:1 compression ratio/7 quart oil pan/650 CFM carb/TKO500. My oil temperature seems to stay within about 15 degrees of my water temperature. Cruising at speed it stays about 15 degrees lower than the 180 the water temp stays at. When I stop at a red light the oil temp will creep up to about 200/205 while the water temp creeps to 185/190. My engine has about 450 miles and is just breaking in. I am not sure if this is good or bad but that is my experience thus far. My car is used for cruising and I do not intend to track the car.

I am interested to see the direction this thread takes.

[Gumball]

My 347 with a 650 cfm carb has a 195* thermostat and runs spot on at that coolant temp after initial warm-up. I have a thermostatic controlled electric fan and that keeps it within a few degrees (Cel on my Smiths gauges).

The oil under normal driving runs about 140* - 175* and only gets in the 195* - 200* range when idling in traffic on really hot, summer days or running it hard in similar weather.

I do not use an oil cooler and my gauge (also Smiths) is mechanical with the bung in the sump area of my 7 qt Canton pan.

If it's running too cool, then I sure don't know how to make it any hotter.

[NAZ]

140-degree oil temp is far from being too cold. Most engine wear is attributed to cold starts where the oil is cold and viscosity is high enough to impact the flow of oil through tight clearances. You can find reference to this on some of the oil company websites. If you live in the Arctic you would be concerned with cold oil. In PA, not so much. Here in Northern AZ it gets well below zero in the winter and our vehicles start and run in that temperature and vehicles last as long as they do in sunny California, or Huston, or Miami. I've owned a lot of cars & trucks and worked on many more as a professional auto technician and have never come across a manufacturer that directs owners to maintain a minimum oil temp before driving. If someone tells you different ask them to provide a reference so you can read it yourself.

[Jeff Kleiner]

RPM drives oil temp to a large extent. Cruising on an 85-90 degree day I rarely see >160 but a 50 second autocross run with it running between 5-6,000 RPM will bring it to 230 degrees.

Jeff

[CraigS]

Where is your oil temp sender?. My 351 had it on that oil pressure extender near the filter. It always ran similar to yours. When I did the 408 I moved it to the oil pan. Whoa...on that first drive. Now normal in the summer is about 190 normal driving 40-60 mph which goes up to 210 either at 75mph or in traffic. Even saw 230-250 a few times in traffic. Coolant temp is 180-195 if I forget to manually turn on the rad fan. 195 is the fan temp sender spec.

[AC Bill]

Wide-range viscosity oils were designed to allow for lubrication when the engine was at lower temps. I wouldn't fret to much unless you are using a heavier single weight dino oil.

[JIMOCO]

Thank you all for your thoughts. The sender is about an inch from the bottom on the drivers side of the oil pan. Radiator fan comes on at 180 so the coolant temp is usually stable when cruising around. Using 10w/30 conventional oil.

I am amazed by the wide range of answers. All have been very helpful and the logic of the winter temps helped me get comfortable with the temp reading I'm getting. Driving days are numbered here in PA as we get into the late fall and winter months. While the car is hibernating, I am thinking that I will take the original sender, connect it to the leads, put it in a pot with a cooking thermometer, heat the water and see if I get the same reading on the gauge. Since my sender seems to be in the same location as CraigS, I think this additional test is necessary to verify that I am getting a true reading.

This forum has always been a great resource for me. Thank you for your thoughts and generosity with you time. All additional comments will be very welcome.

[Bob Cowan]

Studies done in Alaska show that oil temps below 160* significantly increase cylinder wall wear.

Look at temperature and viscosity charts. At those low temps, your oil has significantly less viscosity than I'd like.

Tribologists design the oil additive package to work correctly at a certain operating temperature range. Modern engines run a lot hotter than they used to for emissions reasons. So modern oils are designed to operate in those upper ranges.

During normal cruising and driving, my oil would be about 5-10* above coolant temps - right where I wanted it to be. I used stock Ford bearing clearances, and 5W-30 synthetic oil. Do a quick Google search on oil operating temperatures.

You don't say if you have a cooler or not. If you do, it's got to go.

[johngeorge]

Racing my engine oil is around 250deg. That is 4000-7000rpm for 30-45min. If we get a double-yellow it will cool down to around 200 or so depending how long the yellow is. I don't run an oil cooler, but do run Mobile One synthetic, and change the oil after every 2 race weekends.

[JIMOCO]

I don't have an oil cooler installed. It appears that there are two explanations for the cool temp. Either my car runs cool or the gauge is incorrect. I will conduct some further testing and report back.

[johngeorge]

My oil temp sensor is inline with the feed going from the remote oil filter to engine. I'm sure it's reading higher then if sensor was in the pan. On the street it should be about the same temp as water temp. 180deg water temp and 160deg oil temp when sensor is in pan sounds about right

[NAZ]

JIMOCO, after rereading your original post I think I know what some folks on the other forum were concerned with regarding too low of an oil temp. It's not a lubrication issue but a contamination issue. As you know, combustion byproducts make their way into the oil through the piston rings. One byproduct of combustion is water vapor. Motor oils are formulated to deal with contaminates but there is a limit to what they can handle, therefore, we change our oil at a point hopefully before the contaminant levels in the oil become a problem. Water vapor will condense to a liquid state in the oil and combine with sulfur to produce sulfuric acid. This is very corrosive to the engine and causes cylinder walls to rust. You see this damage mostly in diesel engines that do a lot of idling or short runs (like construction equipment) where the oil temps are low and the oil change frequencies are extended. It’s also frequently seen on engines that are stored for long periods or seldom run – generators, boats, and airplanes. When oil temps are higher, especially above 212F there will be less water build up in the oil. We used to use a simple crackle test (Google it) to confirm the presence of water in oil. So if your street toy runs lower oil temps you probably don’t want to extend your oil changes like in your family ride. For me, I’d take the 140-deg oil temp over extended oil changes. Remember, one of oil’s primary jobs is to cool the engine. In fact I’d recommend going away from a mileage based oil change and to a calendar based change for any vehicle that is not used frequently and year round. On aircraft engines we used to change oil every 50-hrs or 6-mths which ever came first. For motorcycles that are put up for the winter we pulled the plugs and used a fogging oil to coat the cylinders to prevent corrosion.

[JIMOCO]

So far the consensus seems to be that the low temp is acceptable. After break-in I have been changing my oil at 1,500 to 2,000 mile intervals. I now have 5,000 miles on the engine. This morning I disconnected the harness and attached the original sender that I once thought was defective (before replacement it gave me the same reading as the new one). I put a pot of water on the stove with a meat thermometer and brought it to a boil. Went back to the garage and inserted the tip of the sender into the pot and watched the gauge. The gauge quickly read within a few degrees of the meat thermometer. Recognizing there may be inaccuracies in either the meat thermometer or the gauge (+ or - a couple of degrees) I concluded that getting similar readings told me the gauge was operating properly. The NPT thread size is different on the pan than the sender so I used an adapter. I believe that the sender is sufficiently inside the pan to get a reading. So, I guess that I should get comfortable with the low oil temp. Thanks for your help everyone.60850

[rich grsc]

I see your problem. Using that adapter, doesn't allow the end of the temperature probe to stick out into the oil. If you remove them together, you will see that the tip of the sender is flush with the adapter, you are getting an incorrect reading. What you have is a reducer bushing, you need a close bushing. Hard to find, I had to make my own.
Looks something like this.

60851

[JIMOCO]

I going to give the reducer bushing a try as rich grsc recommends. I made a close bushing from a typical brass reducer that will allow more of the sender to extend into the oil pan. I figure it is worth a try and will install it later this week. Thanks for the suggestion. 61005

[rich grsc]

Thats what I did to make my own. Certainly hope it helps.

[Paintwerks]

I know it's not a Ford engine, but the supercharged 6.2 LSA in my Absolute Pace AC Cobra sees the oil temp running at about 220-230F in daily driving. It got up to 265F on the track. Modern synthetic oils have no issue regularly running even at 300F, and Mobil 1 is claimed to have full protection right up to 500F.

https://mobiloil.com/en/article/why-the-mobil-advantage/mobil-1-performance/mobil-1-high-temperature-motor-oil-protection

I always let my car get up to oil temp before ragging on it. As the others have said, too cold an oil temp is bad for the motor.