got in a discussion about oil life, and temperatures today at work. one of the motorcycle racer guys said that once oil passes 200 the life starts to get used up. 250 and it's time to think about changing it.

never having paid much attention, i watched mine on the way home. after a spririted run to close to 2X the speed limit, the oil temp went to 214, and didn't drop like water temp does. 65 degrees out, water at 187.

what is the normal range of oil temps in normal driving in cool conditions?
what controls the oil temp on our cars - is there a thermostat - what is it's opening point?

thx
mike

 

It's synthetic oil, so temp threshold will be a lot higher than conventional oils. I change at around 3k, regardless of monitor life. My temps get up to about 230 on spirited drives and then they drop and fluctuate around 210-220. Folks that do HPDE's usually will see higher than 230 temps.

 

When I run Mobil1 the temp under normal hard driving stays around 210-215, when I run Amsoil it stays 205-210. My dic is always set to show oil temp. Its hardly ever under 200.

 

210 even in heavy traffic here - Mobil1 5-30 - I change the oil often, cheap insurance.

BTW- dont ever get on the throttle unless the oil temp is at least past 160. I heard the ingredients in the oil aren't fully active until that threshold.

 

Most synthetic oils today will last for a very long time. They are also resistant to breaking down at high temps, I wouldn't worry until the temps run at about 240-250.

My uncle went 12K on his Mobil 1 before he pulled the motor for a 404ci LS2. He had 2 track days and more than a few passes at the strip and the oil looked fine. Me personally I would run the oil out to 7,500mi or maybe longer before changing.

 

Mike,
There are several issues here. I don't think its the heat that "uses" up an oil, but the shear load at high heat can break down the hydrocarbon or man made synthetic chains that make up the basestock of the oil. This can happen faster than you might think. To see this point illustrated, read the section on page 9 of this motorcycle report on viscosity shear:
AMSOIL Motorcycle Oil “White Paper” (1 MB pdf file)

Here is a quote for those who can't download that file:
"The results point out significant differences between oils and their ability to retain their viscosity. Within the
SAE 40 group, 36% of the oils dropped one viscosity grade to an SAE 30. Within the SAE 50 group, 40%
dropped one grade to an SAE 40. Most of the oils losing a viscosity grade did so quickly, within the initial 30
cycles of shearing.
It should be noted that both high and low viscosity index oils exhibited significant amounts of shear and viscosity
loss. Two of the oils with the highest viscosity index, Torco T-4SR in the SAE 40 group and Yamalube 4R in the
SAE 50 group, had the largest drops in viscosity of all the oils in their respective groups. Torco T-4SR sheared to
a SAE 30 and Yamalube sheared to a SAE 40. Valvoline 4-Stroke SAE 50 and Castrol V-Twin SAE 50 had a
comparatively low viscosity index and they too lost significant viscosity, shearing down to SAE 40."

The other issue is viscosity which changes dramatically with temperature. Our engine is designed for an oil with a viscosity in the range of 10-12 cSt, which a 30 weight is at a temp of 212F, our car's normal operating temperature. But at 300F, a 30 weight's viscosity is in the range of 3-4. For this reason, those of us running our cars on the track where we see very high temps, we use higher viscosity oils.

 

And some of us installed an oil cooler because when they hit 285+ they freeked out and stopped having fun on track

Now the oil temp is staying at a nice even 235 when being pushed and plenty of oil pressure

Mike 210-220 on the street/highway is very common and not an issue. Just do your regular oil changes and you're ok.

Graham

 

I've heard/read somewhere the same thing about the 160 temp.

 

You actually want the oil to hit over 212 at times as this burns off moisture and other crud- so a little over 212 is actually good once in a while....

 

Personally I also use the 160 temperature before I run the engine up, but not for the chemical properties. Below 160 reading on the oil temp, I figure the internal engine parts are not fully heat soaked yet, that means they may still be expanding, that means piston to cylinder wall clearances may not be completly sealed the best they can be. The heavier iron components (like the crank, piston rod bearing ends, lifters, pushrods, etc. may also be still in the expansion stage. Additionally, I really don't know how well the oil can flow below 160, and at higher RPMs the top end of the engine needs oil, pressurizing it I don't think is the problem, it's how quickly the oil can release from the top end components and return to the oil pan to be picked up again. That's probably why Chevrolet recommends adding an extra quart when tracking the car, to ensure there is sufficient oil in the system to prevent cavitation of the engine oil pump caused by starvation because most of the oil is still in the top end of the engine under high RPM. Add that to high G cornering forces, and it's a recipe for trouble.
Anyway, those are my thoughts, for what they are worth this morning.

One more note, while getting over 212 will hasten the reduction of moisture that may be present in the crankcase, duration of warm to hot oil is the key to giving it time to evaporate, and be removed by the PCV system. 212 is the boiling point, but any temperature above the ambient dew point for the day will work, just give it time.

 

I thought that the car had an oil cooler. It's hard to believe that my 86 Saab has an oil cooler and my high-tech Z does not.

If there is no oil cooler, what cools the oil, just contact with the water cooled components?

Thanks everyone for the insight. I'll be sharing it with my bike riding engineer friends - sure to stir up some spirited conversation.

mike

 

The engine oil cooler for the Corvette was dropped in 1992 when the LT1 engine was designed to use Mobile 1 synthetic. Because the synthetic oils have a higher temperature tolerance than dino based oils, the oil cooler was deemed unneccessary. The Corvette still has a power steering cooler and of course the automatic trans have a cooler. I think the C6 z51 option also now includes a transmission oil cooler for the 6spd, but no engine oil cooler.

 

The wait till it's warm.Over 160 oil. Is something I do everytime before she sees over 2 grand or so. Mine runs at 192 water and when it gets warmer my fans are set for 208.

 

My 1993 Formula Firebird had one. And there is no Mobil one motor
produced by GM. Is because GM gets the free oil and Mobil gets the the big advertising.They stick an Mobil-one cap on it. I dump the Mobil-one first thing. Because it's not that
good. In Any Ls-1 ls-2 ls-6. It has a low volitility,
and burns off.
Many synthetics work MUCH better in these motors. Including the Lt-1's

 

That's a good number and near what I use as well. But, as explained well above by Z06vettepilot, there isn't anything in the oil that is "activated" at those temps, but there are other issues, primarily that the oil is very thick when cold. Most people don't really realize how much so that is. At 100F, a typical 5w30 has a viscosity about 5-6 times higher than at 212F.

 

Mobil 1 is claimed to be good to 400 degrees. On track days I always hit 300. Both on my Z06 and my previous '00 hardtop.

 

The temperature displayed is not the temperature at the journals/bearings - it is about 50 degrees hotter there than what is displayed on the gauge.
Mobil 1 is very good oil otherwise the hand built AMG engines, Viper, Aston Martin, Porche, McLaren, would not be factory fill. Especially the AMG engines and McLarens- if Amsoil, Royal Purple or RedLine was better you can be sure they would be used in those ultimate engines. These builders do not care about free oil !

 

The issue is not whether the oil is "good" to 400 degrees, the issue you should be concerned about is the oil's viscosity which goes down as temperature goes up. At 300F, a typical 30 weights vicosity is only 30% of that at 212F. For this reason, one of the key parameters of an oil's suitability for track use is its High Temp High Shear (HTHS) rating. The High Temperature/High Shear Test measures a lubricant’s viscosity under severe high temperature and shear conditions that are similar to severe service applications in an engine. In order to prevent wear, it is important for a lubricant to maintain its protective viscosity level under severe operating conditions.

Contrary to the feelings of Skeet, Mobil 1 doesn't perform best in this area. Here are some HTHS ratings direct from the manufacturers websites. Note Royal Purple doesn't share this info (which is one of the reasons I switched to AMSOIL vice Royal Purple) and Redline uses a different test standard.
AMSOIL Series 2000 20w50 – 5.1
AMSOIL High Performance 20w50 – 4.9
Mobil 1 EP 15w50 – 4.43
AMSOIL High Performance 10w40 – 4.3
Mobil 1 EP 10w40 – 3.9
AMSOIL European 5w40 – 3.7
Mobil 1 0w40 – 3.6
AMSOIL Series 2000 0w30 – 3.4
Mobil 1 EP 10w30 – 3.21
AMSOIL SAE 10w30 – 3.2
AMSOIL SAE 5w30 – 3.2
Mobil 1 10w30 – 3.14
Pennzoil Platinum 10w30 – 3.1
Mobil 1 5w30 – 3.09
Mobil 1 EP 5w30 – 3.08
Pennzoil Platinum 5w30 – 3.0
Mobil 1 0w30 – 2.99
AMSOIL XL 5w20 – 2.7
Mobil 1 5w20 – 2.62
Pennzoil Platinum 5w20 – 2.6

At my last two races I used AMSOIL High Performance 10w40 has it has a HTHS rating near that of the Mobil 1 EP 15w50, but will provide lower friction losses (hence more HP) since it is a 40 weight vice a 50 weight. Note, no 40 or 50 weights meet the owner's manual requirements.

 

The RP Synthetic oils score typically between 3.2 - 3.5 on HTHS. I got that info simply by emailing their engineering folks and asking.

If your car is under warranty then you should be using an API certified and licensed oil. Most or all of RedLine aren't. And many of Amsoil aren't, just their XL flavor which scores no better than Mobil 1. You can go find that out yourself at the API website.

I just got my report from Blackstone Labs on my used RP 5w-30 using Mobil 1 Oil Filter. In an 02 Z06, 4665mi on oil, 2 autox and 2 track events, rest commuter miles. Track events occured in GA in 80-90 ambient temps. No oil cooler at the time. Oil temps constantly between 260-280deg. The lab report shows the oil is in very good shape and I could continue to use it if I wanted to. Also oil and air filter were doing their job. No gas, coolant, or other crap in the oil that doesn't belong there. Normal wear on the engine all levels well below average.

Moral of the Story: All these vendors hype up the things they do best and make it sound like their test is the most important one of all. Get Mobil 1, Amsoil, RedLine, Royal Purple and you'll be fine. If you plan on ragging your car on a road course then fancy oils and which one lasts at 400deg isn't the answer. The bottom end of your engine won't. Add an oil cooler and keep the oil from getting that hot in the first place. Same common sense for cooling. Doesn't matter if you use Green/Orange/Whatever coolant. Get it under control.

Note: This is not intended to start an oil flavor pissing contest. I have no affiliation with any oil company or vendor. YMMV.

 

I was out yesterday and checked the oil temperature, it was running at 204 degrees. The coolant temp was at 194 degrees, unless I was in traffic.

So it looks as if there's a 10 degree difference in my Z06 at normal cruising speeds.

Bob