DavidEverly

What should the typical oil temp be? in my 81 the water temp is running about 180-190 yet my oil temp gauge says about 100. I would think the oil would be atleast as hot as the water. Might be needing a new oil temp sending unit but thought I would check with you guys(and Gals) first..

thrilher

i have a '79 and other day i was driving it my water temp was at 100. I unplugged it from the block rubbed it as best i could beside the road plugged it back in and it went back to normal operating range

bashcraft

The oil temp should run slightly higher than the water temp. 230f-250f is preferable. This will allow any moisture that has accumulated/condensed in the oil to boil off.

Xakk

Mine generally runs 10-20 degrees hotter than than the water temp.

RIJVETTES

the guys are right. jim

norvalwilhelm

I have a good autometer mechanical water temp gage and a matching oil temp gage. My oil temp is taken in the pan and it always ALWAYS is about 20 degrees below the water temperature.
My desired water temp is 190 and the oil sits at about 170.
I have NEVER seen the oil temp higher then the water temp.
I also find that it takes about 15 or 20 minutes for the oil temp to even start reading on a 140 minimum gage.

CA-Legal-Vette

Interesting. This has been my observation as well and always assumed that my temperature readings were inaccurate. I would have thought that the oil should be hotter as well but perhaps it takes a long time to get there.

540 RAT

You need to have an oil temp of at least 212*F to boil off condensation, same as on your stove at home. If your oil stays colder than this, the water from that condesation, and sulfer combustion byproducts will combine to form sulfuric acid....not something you want in your oil to say the least. I'm surprised some of you guys see oil temps colder than coolant temps, since typically it will be the other way around. Its not uncommon for oil temps to be something like 50* higher than coolant temps in a setup with no oil cooler. And if you run it hard, oil temps can get much higher than that. That's why a 160* thermostat would generally be preferred over no thermostat. That way you can get coolant temps up to at least where the oil temps will usually get to the 212* to burn off that water. The reason we have always heard that short trips where the engine doesn't get up to temp are worse on an engine than highway driving, is because those short trips don't get rid of the water in the oil, where highway cruising will. I would recommend some investigation to see if those gauges are reading correct, because those backwards temps don't sound right. Don't just assume because its an Autometer that it is correct, it could be defective or have too much resistance at a connection, etc.

turtlevette

the oil temp is more related to how hard you drive. Oil coolers are normally only required for sustained high rpms such as road racing or driving the autobahn.

Norval's oil temp stays low because that big blown engine hardly has to turn any rpm to get him around even during "spirited" driving.

A cool water temp is no gurantee of a cool oil temp. For example my jetboat was cooled from lake water (open system) and i could turn up the flow to the point where the intake manifold would be stone cold under sustained full throttle operation at 6000 rpm. The oil temp would still climb to up around 300 degrees. I had to install a water to oil cooler to keep oil temps under 230 for sustained 6000 rpm operation.

bashcraft

But the fact remains that a minimum oil temperature needs to somehow be maintained, or else more frequent oil changes will be required.

I had a C4 that the oil temp would quickly go to 230f and pretty much stay there. But during sustained high speed driving, the temp would slowly rise. I always slowed down when it went above 280. Heard that bad things happen to oil around 300.

norvalwilhelm

Both gages are the copper tube type, no electic sending units and what can I do if the motor is sitting at 190 and the oil is sitting at 170?? I have no oil cooler, that's just the way the temp sits.
I do control the fans and I will let the motor creep to 205 in town stop and go traffic and will see the oil temp climb to 190 but then I turn on a fan or get clear of traffic and within a block or 2 both the oil and water temp are back down.
I have run say 50 miles at 85-90 mph, no fan whatever turned on, temp stablizes at 193 or so and the oil sits close to the 170. The gage moves freely in stop and go traffic and the oil temp really rises and falls with the speed of the car but never does the oil temp pass the water temp.

norvalwilhelm

Your boat oil pan would not be in the wind. My 10 quart oil pan is hanging down and within a mile of two of open road the temp drops right back down to it's normal running temp of 170
You are right that blown big block loafs along at 80 or 90 at about 2200 rpm and NO fans are required to keep it cool.
I do run my high capacity water pump at 30% overdrive and do run a big aluminum rad.

theoUK

Norval, I'd feel happier with oil temps being quite a bit above the coolant temp, someones already mentioned 212 or above, that's more like it.

As turtle said, the oil temps are governed mostly by how hard you drive. Well, specifically it's the engine speed that directly influences the oil temp, because this dictates the rate of heat you're dissipating into the oil at the bearings/rubbing surfaces. Perhaps you're just not getting enough sustained high engine speed to get a decent oil temp. If you're turning only 2000-odd rpm at cruise, then I guess that might explain the low oil temp, but I'm not sure if it explains it being as low as 170F. Where are you measuring the temp of the oil? Do you have a sender screwed into the sump drain plug or something? The outer regions of the sump can remain quite "cool" for a long time through the warmup, specially if located a long way from the pump pickup, in a region where there's not much movement/mixing of oil. Of more "use" is a measurement of oil temp up at the filter, as this is closer to the main gallery/feed temp, and therefore more representative of what's going into the engine.

Still seems odd to me that the oil is running cooler than the coolant, maybe your engine is just never being given enough of a "screaming"!

norvalwilhelm

My oil temp is taken about the center of the pan on the passengers side about 1 inch up from the bottom. When I built the pan I installed a bung for the oil temp bulb.
As for not driving fast enough I break every speed limit going most of the time. Cruising at 80-90 in a 60 is normal and while I would gladly drive alot faster cops don't agree.
The big block does loaf along like Turtlevette said with 308 gearing and .68 overdrive. Acts like a 2.1 rearend.

theoUK

hehe
Well, like i said, it's more the engine speed that's the issue, rather than the car speed. The speed of the car comes into play with respect to the amount of heat coming out of the oil from the bottom of the sump, the engine speed dictates the heat going in to the oil.

But with that gearing it seems the engine is practically ticking over even at pretty high vehicle speed, so you're got a fairly low heat input and a relatively high out-flow, so maybe that's why the oil temps are low. Either that or the gauge is off! I think the stock place for the oil temp sender in the later vettes is up on the filter housing, so maybe all the housings have a tapping here? It'd be interesting to see what kind of temp you are seeing up here.

bashcraft

I would venture to say that 10 quarts of oil is going to take much much longer to heat up than 5 quarts would.

theoUK

Yeah, about twice as long, funnily enough! Thats a good point, i bet it takes ages to actually settle out to a steady temperature with that amount of oil in the pan. Jeez, that's nearly ten litres (can't work in quarts, being a Brit!) - that's up around the diesel truck kind of fill quantity!

bashcraft

Not to mention the oil is sitting in the pan twice as long before being circulated again. Much more time for it to cool down. Plus the pan must have a bigger surface area.

CA-Legal-Vette

One other note to add to this discusion. Although water boils at 212 degrees F, it doesn't need to be at that temperature to evaporate. If you want proof, look at the bottom of your ice cube tray and notice that these are smaller than those that are fresher. The water is evaporating (sublimating actually) and the air temp is around 5 degrees F, well below freezing. Water will evaporate from the oil pan at pretty much any conceivable temperature of operation, just not as efficiently.

rotgirl

A LOT of different factors affect oil temp, ie: WHERE oil is sampled, is oil pressure optimal, is H2O/glycol cooling mix optimal, state of corrosion present in oil passages, and weight and viscosity of oil used. Remember that oil has many functions in an internal combustion engine.
1) Reduces friction
2) Seals and Cushions
3) Cleans inside of Engine
4) Protects against corrosion
5) Performs Hydraulic Action

So before you make any drastic changes, ascertain that everything else is within manuf. specs.

RD, piggy-backing on rotgirl's good name