[steve25]

Here’s a very interesting list of the life of mineral based oil at a given temperature.

Take note of how the life expectancy tumbled from 1.56 years to 1.16 years with just the change from 190 to 230 degrees!

Makes me want to jack up the daily driver right now and change the rear end lube, lol!

Sorry this should not have up loaded sideways like it did!

[indymanjoe]

where did you find this? Have a link? Another forum i frequent is having arguments over this very subject.

[Steve C.]

Another....

Heat-related lubricant failure
In the late 19th century, the Swedish Nobel Laureate Svante Arrhenius discovered a direct relationship between temperature change and the chemical-reaction rate in fluids that he put into an equation known as the Arrhenius rule. As summed up in the following statement, this rule is used in the lubrication field to express the temperature-change-dependent failure rate of oils: “For every 18-deg. F (10-deg. C) increase in oil temperature, the lubricant’s life is reduced by half.” Conversely, reducing oil temperature by the same rate doubles the lubricant’s life (see Fig. 1).

https://3q0ds8402hawyzjwb3qrnh43-wpe...2.05.49-PM.png

Source:

https://www.efficientplantmag.com/20...t-temperature/


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[Steve C.]

Synthetic lubricants generally last longer at elevated temperatures than their mineral-oil counterparts.

Graph here:

https://www.machinerylubrication.com...edict-oil-life



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[77 TRASHCAN]

The old Mobil One commercial with the 2 frying pans that had oil in them, told me all I needed to know about synthetic motor oil, years ago....although I guess there was controversy about the exact formulation of Mobil 1, back then!!!

[steve25]

I got this chart from the tradecraftspecialties.com site.

[Steve C.]

"... I guess there was controversy about the exact formulation of Mobil 1, back then!!! "

Still exists. Want to open up a bucket of worms, just go to 'Bob Is The Oil Guy' website and seek whether Mobil 1 is an ester base synthetic. And further if Mobil 1 oil is really Group IV and or Group V or if it is really a Group III Conventional oil.

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[Sirrotica]

Pennzoil Ultra Platinum™ keeps pistons up to 25% cleaner than Mobil 1 and Pennzoil Platinum® keeps pistons up to 8% cleaner than Mobil 1.

That oughta get the Mobil 1 users riled up...........

[i82much]

Originally Posted by Sirrotica

Pennzoil Ultra Platinum™ keeps pistons up to 25% cleaner than Mobil 1 and Pennzoil Platinum® keeps pistons up to 8% cleaner than Mobil 1.

That oughta get the Mobil 1 users riled up...........

i like my pistons how i like my future ex-girlfriends ... dirty with short skirts and a little too much clearance ...

[Half-Inch Stud]

I'm drinking coffee while reading this. Thanks.

[steve25]

I bet I can guess what you use to check that clearance other then Plastigauge, lol!

[Formulajones]

Originally Posted by Steve C.

"... I guess there was controversy about the exact formulation of Mobil 1, back then!!! "

Still exists. Want to open up a bucket of worms, just go to 'Bob Is The Oil Guy' website and seek whether Mobil 1 is an ester base synthetic. And further if Mobil 1 oil is really Group IV and or Group V or if it is really a Group III Conventional oil.

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Yeah I've read that at various places years ago how Mobil 1 changed their base stock back in the late 90's to a lesser base stock. But you also hear that same speech from all the other competing oil companies so it's difficult to weed through it all and find the truth.
One thing that is consistent among all the information I dig up is that synthetics do hold up better to higher temps.
The problem with rear end gear oil is that all of the clutch style posi unit manufactures that I've dealt with over the years absolutely do not recommend synthetic fluids with their units and some gear manufactures don't like it either.

[Formulabruce]

There are mineral based, ash based and completely synthetic baes for oils.
For many years Mobil was ash based, and Only Royal Purple was 100% $ynthetic.
Pure Synthetics are more durable.
Worried about your rear end, or trans ,or engine?
Put some " Motor Kote" in your oil.
Extreme testing has proved its worth.
Reduce friction. https://m.youtube.com/watch?v=88vwUwa3igQ

[Schurkey]

Temperature is one of about a dozen factors in oil life.

Moisture contamination, and fuel contamination, (blow-by contamination) is probably a larger factor.

Consider also that most cars don't have an oil temperature gauge, and those that do tend to have them in the oil pan, while the highest temperature is at the bearings.

All told...oil temperature doesn't mean much to me provided it's high enough to vaporize moisture into the PCV system, and low enough that I don't find coked-up passages at rebuild time, or low oil level due to volatile compounds in the oil boiling out. I used to see 300 degree oil temps with my "old" boat engine when revved up under load. After a few of those indications, I rebuilt the engine and dug all the rubber water-pump impeller debris out of the cooling passages. Now the oil temp never goes over 180. Even with occasional 300 degree oil temp, I had no undue bearing wear, or burnt oil in the drainback holes or around the exhaust gas crossover.

[Steve C.]

Generic online information...

"Synthetics can safely handle higher operating temperatures without oxidizing (burning) or breaking down. The upper limit for most mineral-based oils is about 250 to 300 degrees F. Synthetics can take up to 450 degrees F. or higher (some as much as 700 degrees F)."

Generic Hot Rod Magazine article on the subject....

"A quality conventional motor oil will tolerate oil sump temperatures of up to 250 degrees, but starts breaking down over 275 degrees. The traditional approach is to try to hold oil temperatures between 230 and 260 degrees."

"A full-synthetic oil will withstand sump temperatures in excess of 300 degrees, and for hard-core professional racing, some oval-track race teams are experimenting with ultra-thin, specially formulated, race-only synthetics operating at 350 degrees or even higher."

https://www.motortrend.com/how-to/en...l-temperature/

OK, some online humor.......

"Here's the problem with Bob Is The Oil Guy Forum.... It's like the oil version of WebMD. With WebMD, if you research your symptoms enough, you will undoubtedly be led to the conclusion that you have stage 4 cancer and will die tomorrow. With BITOG, you'll reach the conclusion that your oil should cause your brand new motor to lock up in the next 50 miles, regardless of what you're using. You will have a hard time going wrong with any of the top-tier synthetics."


Get The Guarantee
https://www.youtube.com/watch?v=dAkSziqGk00


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[steve25]

Helping to keep oil temps in check was also why Pontiac engineers put the dead air space above the exh crossover passage in the 5 and 6 series heads.

[Sirrotica]

About oil temps, and oil breakdown from personal experience. Back in the mid 90s I used to work for a asphalt sealing, and patching company maintaining all their equipment, and trucks.

The blowers they use to clear the debris off of the asphalt before they seal it were 8 HP Briggs engines. They run for hours wide open against the governor at 3600 RPM, and are on asphalt all day long which can be 120-140 degrees. Far from ideal conditions for any air cooled engine, and hard on the oil.

One year when the ambient temperature was higher than normal, we had a rash of those engines blow up due to the piston seizing in the cylinder and breaking the rod in half, then punching a hole through the block. On four blowers I was averaging one blown engine per week. Replacing the short blocks was getting prohibitively expensive.

We first tried heavier oil, (straight 40W) and were changing it every day (8 hours run time) per oil change, we were still killing engines. I opted to place a call to Pennzoil's tech line as I used to be a Pennzoil service station dealer, and had called them before with tech questions concerning race applications, and customer concerns.

As soon as I explained the problem, the tech told me to switch to their synthetic oil, and that would end the problems. I asked about oil change frequency, he responded I could run it 40 hours before changing it. We switched, and the engine problems went away. The synthetic at that time was about 4 dollars a quart, but saving the engines, and down time was well worth the extra cost for their synthetic oil.

That proved to me beyond a shadow of a doubt that synthetic oil could, and would withstand extreme oil temperatures without breaking down. I believe it was before Mobil 1 previewed their frying pan commercial....... I've been using Pennzoil synthetic in all my own cars since then.

[steve25]

You do not see a drop of mineral based oil used in jet aircraft engines, that's enough said for me right there!

[Steve C.]

Similar situation....

Your M1-series Abrams tank’s AGT1500 engine can last a long time with proper care. How long? The goal is a minimum of 1,400 hours.

But with proper maintenance and operation, engines can keep going for much longer than that. One requirement.... Use high thermal stability oil (HTS) in most circumstances. But check the TMs and LOs for the right oil at the right time.

Mil-PRF-23699 HTS (High Thermal Stability) turbine oils are industry standards for commercial and military aircraft applications. These synthetic oils are favored for their superior thermal and oxidation stability over a wide range of operating conditions.


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