When it comes to engine oil, maintaining the right temperature range is key to longevity and minimizing internal wear. That’s because engine oil relies on its viscosity—the thickness of the liquid—to create a protective barrier between moving parts.
But the catch is that viscosity isn’t constant; it changes with temperature.
If you’re running dual weight oil, such as 5W30, the 5 is the cold viscosity while the 30 is the warm viscosity. This allows the oil to circulate quicker and easier in low temps when cranking, but thicken up to protect the engine as it warms. That is the main reason why frequent short trips are rougher on engines and why you’re supposed to let an engine get to running temperature before driving it hard.
In addition to lubrication, oil also serves to transfer heat away from engine components. If the temperature becomes excessively high, oil viscosity can thin to a point where the lubrication barrier can begin to break down, increasing wear and the risk of serious engine damage. On the other end of the spectrum, cold oil viscosity doesn’t flow quickly through the engine and can cause excessive frictional drag on the bearings and cylinder walls, which also leads to accelerated wear over time. To add another layer to this, the internal combustion process produces water, sulfur, and other byproducts that can form acids that damage bearings and getting oil to the right temperature range helps manage these contaminants.
So, we want our engine to regularly get warm enough to burn off water and other contaminates, but not so hot that our oil starts to break down. On the low end, that means we want the oil to get warm enough to evaporate out the water and contaminants. We spoke to oil experts at two leading companies, and both agreed that if your oil reaches around 180 to 215 degrees routinely, it will be fine.
Outside of extreme winter conditions, that’s usually not a problem for street cars as they’re engineered to reach a temperature set by the cooling system thermostat. If you are in extremely cold weather or taking frequent short trips where your engine struggles to get up to temp, just plan on shorter oil change intervals. Both of our industry experts agreed that even in those conditions, if you’re using quality oil and the oil is hitting at least 160 degrees, you’re fine. Just don’t run it hard at those temps and use shorter oil change intervals of around 3,000 miles.
Where temperature can become a problem for performance driving is on the high end where sustained high rpm use sends oil temperatures well above the standard driving range. Quality conventional motor oils can easily handle oil pan sump temperatures up to 250° F, but begin to degrade above 275° F. Many full synthetic oils can withstand sump temperatures up to 300° F, which is one reason they are often recommended for extreme use. These are temps that you’re very unlikely to ever encounter in normal street driving but can occur if you’re running the engine hard for extended periods.
In either case, our experts agreed that the ideal driving around temperature range for most oils and most cars is around 190 to 230° F with roughly 200 to 215° being a sweet spot. This is hot enough to remove water and other byproducts from combustion, but well below the range where viscosity is going to become an issue. For dedicated race cars running high viscosity and high temp racing oil, these temperature ranges can shift upwards to around 275 to 300° F, but keep in mind that those are limited lifespan engines.
This is where oil coolers come in. Just like a radiator, an oil cooler acts as a heat exchanger that creates increased surface area that air can flow across to cool the oil down as it moves through the tubes in the exchanger. In the case of an efficient oil cooler, that temperature drop can be 30 to 50 degrees. That’s enough to take engine oil from the critically high temperature zone back to the safe zone.
By now, you’re probably wondering about your current car and whether you need an engine oil cooler to stay within the ideal engine oil temp range. The good news is if you have a street driven car that is never used for extended periods at high rpm, such as road course style track day events or high speed off-road driving, the odds are that you do not. A typical street car running quality modern engine oil only needs the radiator and cooling system plus the oil pan sump to stay within the required temperature and viscosity range. Even most drag racers and autocrossers don’t bother with engine oil coolers since their runs are usually too short to spike engine oil temps excessively. It’s when you start pushing things hard for extended periods that you might be moving outside of the safe range.
That can happen quickly too. Most track day sessions, like those our dual-purpose street/track S197 Mustang project car runs, are typically in the 15 to 20 minute range. Being hard on the throttle for that long can exceed the cooling system’s ability to keep the oil within ideal temperature range, especially on a hot day. We’ve seen it happen many times at track day events. For those without an oil temperature gauge, one of the first indications that the oil temp may have gone to concerningly high levels is significantly lower than normal idle oil pressure at end of a session.
Unfortunately, our S197 Mustang wasn’t originally equipped with an oil temperature or true oil pressure gauge, so we’ve been somewhat blissfully ignorant of exactly where our post event engine oil temp peaked and how low the pressure dropped, but we know it isn’t good. In addition to an oil cooler kit, we’ll also be adding water temp, oil temp, and oil pressure gauges so we can see exactly what temperatures and pressure our engine is seeing on and off track.
Summit Racing has numerous oil cooler kits, including one from Improved Racing that is exactly what our track focused Mustang needs. Follow along as we install and test it on street and track.
