Oil & Correct Operating Temperature

[Dominic]

quote:

---

Originally posted by Patman:
I too worry about the effects of racing my car with cold oil. In order to run the best ET in an LT1, a one to two hour cooldown is often the best thing. But I wonder what harm I'm doing to the engine by running it so hard on cold oil?

---

Just like oil takes a lot longer to heat, it takes a lot longer to cool. So while your coolant mightve dropped to 140degrees in 1.5hrs I guarantee the oil is still fairly warm

I usually take a quick lap around the warmup circuit before racing mine after letting it cool off just in case, I have so far noticed no drops in ETs from doing such a thing.

If you want your engine to run cool you need a 160 stat and a fan switch - kick the fan on and idle on up to the stage lanes. By time youre ready to go that coolant will be in the 165/170 range ready for action, and the oil will be up to temperature also ready for action.

 

[Patman]

I used to run a 160 thermo in the 95 Trans Am I used to own, but with this one since I drive it all year round I like to stick with the stock thermo, since I don't feel it will get the oil warm enough in winter with a 160 (and I don't feel like changing it twice a year)

I just had the car in the dealer to have the heater core backflushed, and they put in a new thermo for free for me, and now I notice my temps run about 5-10F cooler anyways. I'm going racing this weekend in 40F weather, so I'm sure if I cool the car down for more than an hour my oil will be pretty cold. I do worry, however I also want to get that perfect elapsed time too, and these LT1 engines run best when cold (mainly because the intake heats up so much)

 

[Al]

quote:

---

Originally posted by Quattro Pete:
The oil in my 1.8T engine reaches approx. 180F after about 20 minutes of driving during winter (outside temps. in the 30s and 40s), and after about 15 minutes of driving during summer.

Also, during winter, my oil temp pretty much does not go above 180-185F, and in summer, does not go above 200F. I've been told by a number of people (with 1.8T engines) that these temps are too low, and that my temps should be in the 200-225F range. Apparently, that's what their temps are. Do I have anything to worry about? Thanks!

---

Welcome to the boards!!

I personally would not worry about it. This is a very slight difference. Besides- depending on the brand and grade of oils, viscosities can vary quite a bit. I mean, really, we know that an engine can tolerate anywhere from a 2- wt to a 50 wt.!! And we still here argue over which is best

 

[Al]

I meant to say "20wt. to 50wt."

Why can't we edit our posts when we make a mistake???

 

[Mark in NY]

Oh my, I cannot believe that all you anal retentive oil guys ( and I am one of you to be sure(( Thanks for this site Bob)))do not show as much interest in oil temp gauges as you do in oil analysis kits. One look at a temp-vis chart will immediately show that 25 deg F to 210 deg F temp range (real world oil environment) has a one-hundred fold more influence on viscosity than one SAE grade does! What I learned when running street and roadrace-track only (SCCA)vehicles with oil pressure AND TEMP gauges-
1- you get to appreciate the fact that water temp is a regulated temp while oil temp is a much greater variable. Water temp will stay at a nominal 190 degrees these days and oil temp can be anywhere from 160-220 plus depending on ambient temp and fuel flow (heavy foot eh?).
2- As suggested in previous posts, the oil cooler can indeed be an oil warmer during the warm up phase.
3- Fresh-out of the can oil will display one oil pressure at 180 deg F when brand-new and another pressure after 20 miles of road racing action.
4- Oil temp generally follows water temp minus 10 minutes in street cars but this can vary greatly depending on ambient temp and how much you punish your motor that day.
So fellow enthusiasts, remember this is the information age. If you want an insight into what SAE grade to choose, install an oil temp gauge!

 

[Al]

Good point Mark. I would add the following. A regular old ISO100 oil is 10cST at 100C. Now it really only changes from about 9cSt to 11 cST in the Temperature range of about 188F to 212F. That is less than one API grade. And this is without any multi-vis polymer. The multiviscosity oil would be even less than this. So in that range its not as bad as "100 fold"

However having said that-you make a very valid point. And if one has a vehicle which runs in the upper range of the scale it may be wiss to either get the temp lower or possibly select a 40 wt oil. Certainly food for thought. Also good information about the gauge for oil running 10 degress less than H2O temp.

 

[Al]

One other point where I really don't have an answer: The gauge temp of the Coolant is measured at the outlet of the engine. It is then safe to say that bulk block temperature is probably 10 degrees or so hotter than this. Now oil temprature is measured where??

. If its measured at the oil pump outlet, then its safe to say that the oil temperature in bearings, etc. is not 10 degrees less than water temperature. Also its safe to say that bearing temperature is less than the temperature at the heads which are closer to combustion. Also there is a lot of splash lub at the rings and the oil in the sump is probably a good deal less than the oil in the bearings (as they pick up heat). My point is there are lots and lots of variables here. The range of oil temperatures in different parts of the engine is huge. One other point-Unless you stick an OBDII on your vehicle-you are probably off another 10 degrees on your gauge temp. : My sentra runs at about 185 F in summer, while my sons Cavalier is 215 F.

Enough of this rambling.

 

[Mark in NY]

Right Al, the temp pick-up points on water and oil systems can vary.
One quick followup and the reason why I say a picture is worth a thousand words. There is much discussion about 30/40 wt. and viscosity at 212 deg F running between 10 and 11 or so etc. If you look at the actual temp vs viscosity curves for the full range of oil temp; well, when I wake up tomorrow AM in NY it will be about 40 deg F. My young neighbor next door who buys into the close tolerance engine, 5-30 oil argument and makes fun of me and my "thick" oil will crank over his engine and his 5-30 dino oil will be around (right off the Mobil charts) 350 cp.
Thats right, THREE HUNDRED. So when I say I prefer 0-40 so the operating temp viscosity is around 14-15 instead of 9-11 it should be looked at in the context of the full operating environment that the engine and oil see.

Cheers,
Time for a beer.