Oil temp discussion

railgun · 03-05-2008, 11:24 PM

This topic will not revolve around oil grades/weights, but rather the operating temps. A slight discussion of dino vs synth may evolve around it, but the overall goal is to gain insight on recommended oil temps, why, and theories to support or debunk that previous why.

So scotty305 has the big fat cooling thread, and I noticed the recommended operating oil temp of 195-230. I have a 335i which has, typically, a minimum oil temp of 230, in warmer days, it's about 240. One track day had it sitting at about 290. I had always been under the impression that it was way too hot (not including the track day...duh, that's hot

). Granted, it's a synthetic, but cooler oil is better right?

I had been meaning to talk to the folks at Mobil, or Penzoil, or whoever about this, but haven't gotten around to it yet. But someone had brought up an interesting point regarding temps...

Oil is a lot more resilient that I think we give it credit for. I think it's safe to say that we won't let our motors get into a situation where we hit 300 degree oil temps. But the point that was brought up revolved around getting the oil hot enough to vaporize any moisture/impurities, which is the overall cause of breakdown. At least, over time. That said, at LEAST 212 degrees should be hit to keep any moisture (water) from being introduced and let it be ingested by the motor instead.

Here's where the tricky part comes in. With the massive cooling requirements of the rotary, and the extra part that oil seems to play here, does this theory hold any weight? I by no means am an expert in this field, but the logic is sound. If we were able to maintain a healthy, and constant 225 degree temp, why would we not want to? What disadvantages are there by doing so?

scotty305 · 03-06-2008, 02:32 AM

The axiom I've heard from some drag-racer types was "you want hot oil and cold coolant." From my limited understanding, the hot oil has less friction due to viscosity, and the cold coolant kept cylinder head temps cooler (which kept the intake charge cooler), plus the coolant transfers heat more efficiently than oil. I think I heard numbers like 140F and below for coolant temps, don't recall hearing anything about oil temps. Then again, I think drag guys are a little nuts sometimes, and that might not work for street cars or road-racing. In addition, we don't have nearly as many oil-bathed moving parts (lifters, cams, rods, bearings, etc...) so I'm not sure friction from oil viscosity is such a concern for the rotary.

I remember reading an article about the rotary-powered American Lemans car (the Sportsbook-sponsored Courage chassis, I think), and they mentioned it was difficult to package the huge oil coolers required for the 3-rotor powerplant. It would be interesting to hear from those guys what sort of oil temps they were looking for. I wonder if oil temps are mentioned in the Racing Beat catalog, there's all kinds of good info in there.

SLOASFK · 03-06-2008, 04:32 AM

Quote:

Originally Posted by railgun

cooler oil is better right??

Not necessarily. You want your oil to be at the appropriate temperature. Not above or below. I found this link on another forum discussing oil temperatures, viscosity and weight. It's a great writeup, and anyone who cares should give it a very careful read.

http://ferrarichat.com/forum/showthread.php?t=136052

-xlr8planet- · 03-06-2008, 05:09 AM

On my turbo Civic oil temp is about 190.

When I push it on 5th it goes up to 240.

I will be installing an oil cooler soon. Castrol RS gets too thin at 240 and you inmediately notice the loss in oil presure.

03-05-2008, 11:24 PM	#1
railgun Rotolicious Join Date: Feb 2008 Location: ORD-LHR iTrader: (0) Posts: 60 Rep Power: 17	Oil temp discussion This topic will not revolve around oil grades/weights, but rather the operating temps. A slight discussion of dino vs synth may evolve around it, but the overall goal is to gain insight on recommended oil temps, why, and theories to support or debunk that previous why. So scotty305 has the big fat cooling thread, and I noticed the recommended operating oil temp of 195-230. I have a 335i which has, typically, a minimum oil temp of 230, in warmer days, it's about 240. One track day had it sitting at about 290. I had always been under the impression that it was way too hot (not including the track day...duh, that's hot ). Granted, it's a synthetic, but cooler oil is better right? I had been meaning to talk to the folks at Mobil, or Penzoil, or whoever about this, but haven't gotten around to it yet. But someone had brought up an interesting point regarding temps... Oil is a lot more resilient that I think we give it credit for. I think it's safe to say that we won't let our motors get into a situation where we hit 300 degree oil temps. But the point that was brought up revolved around getting the oil hot enough to vaporize any moisture/impurities, which is the overall cause of breakdown. At least, over time. That said, at LEAST 212 degrees should be hit to keep any moisture (water) from being introduced and let it be ingested by the motor instead. Here's where the tricky part comes in. With the massive cooling requirements of the rotary, and the extra part that oil seems to play here, does this theory hold any weight? I by no means am an expert in this field, but the logic is sound. If we were able to maintain a healthy, and constant 225 degree temp, why would we not want to? What disadvantages are there by doing so? __________________ Rc³

03-06-2008, 05:09 AM	#4
-xlr8planet- RCC Contributor Join Date: Feb 2008 Location: Buenos Aires, Argentina iTrader: (4) Posts: 679 Rep Power: 17	On my turbo Civic oil temp is about 190. When I push it on 5th it goes up to 240. I will be installing an oil cooler soon. Castrol RS gets too thin at 240 and you inmediately notice the loss in oil presure. __________________ www.rx7club.com.ar RX-7 Forum in Spanish I make custom decals. Yes, you can ask me

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03-06-2008, 02:32 AM	#2
scotty305 Rotary Fan in Training Join Date: Mar 2008 Location: Culver City, CA iTrader: (0) Posts: 84 Rep Power: 17	The axiom I've heard from some drag-racer types was "you want hot oil and cold coolant." From my limited understanding, the hot oil has less friction due to viscosity, and the cold coolant kept cylinder head temps cooler (which kept the intake charge cooler), plus the coolant transfers heat more efficiently than oil. I think I heard numbers like 140F and below for coolant temps, don't recall hearing anything about oil temps. Then again, I think drag guys are a little nuts sometimes, and that might not work for street cars or road-racing. In addition, we don't have nearly as many oil-bathed moving parts (lifters, cams, rods, bearings, etc...) so I'm not sure friction from oil viscosity is such a concern for the rotary. I remember reading an article about the rotary-powered American Lemans car (the Sportsbook-sponsored Courage chassis, I think), and they mentioned it was difficult to package the huge oil coolers required for the 3-rotor powerplant. It would be interesting to hear from those guys what sort of oil temps they were looking for. I wonder if oil temps are mentioned in the Racing Beat catalog, there's all kinds of good info in there.