got a 79 f150 and the oil temp is really high. I thought mabe cause im driving slow but even on the high way it stays high. What could be the reason for this.

 

And how did you determine that the temp is high? Not many F150s with oil temp gauges. Depends on the location of the sensor as to the readings you will get. Also, the electrical system can cause higher readings so check the voltage at the sensor and the gauge. The oil temp with normal driving should just about mirror the water temp. An oil with a high viscosity like a 20w-50 will run considerably hotter than a 5w-30 or even a straight 30 oil. Lots of reasons but are you sure you have high temps?

 

Ya, I don't think oil temp gauges came on f150's, unless you or someone else added one later. The stock one in the cluster is an oil pressure "gauge"(it's really an idiot light disguised as a gauge, it only shows "normal" or "low") Though the "normal" position varies from truck to truck, some low, some near the "H" line.

Though if you're sure the temp really is high, you can try running a thinner oil(dissipates heat faster), though in a well running engine that really shouldn't happen(why very few cars and only HD trucks come with them, it's typically not a concern).

Sometimes low oil pressure can lead to high oil temp since it's not circulating fast enough. Make sure you have a minimum of 6 or 7 psi at idle(that's the psi that the gauge will drop to low). Driving it should get up to a minimum of 15 or 20, but 30 or more is best.

Are you sure the motor isn't overheating? Typically if the oil is too hot, the coolant is overheated too. Like labnerd said, the oil and coolant temps are usually pretty close. The oil cools the actual parts, transfers the heat to the block, and the coolant removes heat from the block.

 

No flames but, you guys are off base just a tiny bit. Oil temp doesn't mirror water temp. I have a true oil temp gauge on my truck...I know I installed it. It's a mechanical gauge too. Water temp (in a good truck with no mechanical problems) is going to be constant based on the thermostat. So in our case, around 200-210, but never less than about 195...the factory thermo temp. (this is measured at the thermostat before the water leaves the engine to return to the radiator)

Oil temp in these trucks runs right around 90*-100* over outside ambient. This is at 70 mph, normal driving, no trailer or crap. If it's 50* outside, my oil temp never gets above 145*. Where's the water temp??? 200+-. If it's 90* outside, then yea, they're both around 200*. It takes quite a bit more energy to heat up the oil than it does water.

This also changes really really fast when you add a load like a trailer, or up through the mountains, high rpm, etc. It increases exponentially. But, even though it increases, it's still dependent on OAT. No matter what, my water temp never moves!! I have never seen a water temp above 215* on my truck. (well once when the fans froze up the radiator, but that's another story...)

With all this said, the absolute highest oil temp I've ever seen on my truck, pulling a trailer up through the mountains, was around 220*. That is no where near too hot for oil. Water temp that day was still around 210* max. I don't know if the charasteristics of an older V8 truck would compare, but it shouldn't be off far.

 

I think it may vary depending upon the application and where the oil temp reading is taken from ?

The '02 Z06 my friend has also has an oil temp gauge. I don't know where GM puts the sending unit, but the oil is always within 5-10 degrees of the water temp, after the engine is warmed up anyway.

I've driven it hundreds of times, in all types of weather, and noticed the above behavior every time I drove it.

Just what I have personally experienced.

 

This is the point! A thread started with the statement "really high" doesn't mean a thing without specifics.
My taxes are also high!

 

Ya really, what is "really high"? It's virtually impossible for the oil to get too hot, since for oil to be "too hot" to function as lubricant it would be near like 400 degrees. Unless you have a nuclear reactor under the hood, the engine will turn into a paperweight long before it gets close to that.