Originally Posted by rice_classic
(Post 668365)
Here's my thoughts on oil, pressure and temp. I do not claim these as truths or facts but observations, opinions and recommendations.
The OEM engine is designed to run 100C oil during normal city driving, sometimes a bit more or less depending on conditions. So don't worry about 100C temps, or even 130C (only 266F). Synthetic oil won't break down but if you're going to sustain temps above 120C then you can take two routes:
1: Cool your oil
or
2: Thicken your oil
Neither is wrong or right inherently, the point is to hit the target. The whole point of the game is to match cSt to temp and pressure to RPM. Our engine is designed to be at roughly 8-9cSt @100C and we should have 10 PSI of pressure for every 1000RPMs.
What happens if I install an oil cooler and I'm at 110-120C but I don't have enough pressure? Well, then I need to consider something thicker than the 0w-20. And guess what, our factory manual even states that a thicker oil may be needed for track use.
Basically the reality is that engines like heat, actually they LOVE IT. After all, the hotter they are, the more efficient they become but the problem with that is that at some point things melt, things expand, things go...kaboom. So while engines love heat from an thermodynamic efficiency point of view, their parts do not. So we have to keep our heat in check. The answer isn't always cooler = better. There's nothing wrong with running high oil temps, really high oil temps... ask the Audi Lemans teams or Joe Gibbs or Ferrari. The oil, however, has to be able to withstand it and Joe Gibbs, AUDI Le Mans and Ferrari F1 aren't buying off the shelf oil.
"But rice, if we can run really hot oil and engines like heat, why would anyone install an oil cooler?"
OK, so we know that a good synthetic oil can withstand 300F or 150C for extended durations and we know that amount of temp isn't over burdening the metal of the engine so why seek to lower it? The answer? So we can add more power!!!... or at the very least keep from losing what we have.
Oil is also a coolant for our engines and as this vital cooling fluid becomes hotter it doesn't pull as much heat away from really hot areas. The result is that oil's decreased ability to do its job as a coolant can lead to our engine developing knock and forcing the computer to retard timing... LOST POWER. On the flip side, if we cool our oil very effectively then we might be able to add power like advancing timing or increasing boost without developing ping/knock/pre-det.
So on a track dedicated car or a race car the oil cooler makes really good sense from a maximizing-every-advantage aspect. On a daily driver with an oil you cooler you face the fact that your oil can take much longer to heat up and you could be running your engine less efficiently by over cooling your oil (which thickens it). So yeah, it will do a great job while on track but for 99% of the miles you're going to put on it, it may be overkill.. or it may not. Look at your readings after install, only those will be definitive. Another option is an oil cooler with a thermostat to give you optimal temps all the time.
p.s. I run an oil cooler on my race car, my direct competitor (same car) does not. I use a 30w or a 40w and he uses a 40w or 50w. His engines last just as long as mine (sometimes longer but that's another topic!).
|
