Something to consider, re: thick vs thin oils

[mark pruett]

For all of you getting wiggy about Xw-20 oils in cars as being too thin for effective film strength, keep in mind that jet engine oil (say... Mobil Jet Oil 254) is even thinner, and operates in arguably harsher conditions where inadequate protection can cause much more hazardous situations.

I realize that in some ways, comparing a jet engine with a reciprocating one is apples vs. oranges, but it does point out that a very thin (by automotive standards) can be used in extremely high speed, high temperature applications with great success.

Mobil Jet Oil 254

cSt @ 40C : 26.4
cSt @ 100C: 5.3 (somewhere in the 10W range)

 

[Quattro Pete]

Originally Posted By: mark pruett

I realize that in some ways, comparing a jet engine with a reciprocating one is apples vs. oranges, but it does point out that a very thin (by automotive standards) can be used in extremely high speed, high temperature applications with great success.

High temp, yes. High shear, probably not. And that's possibly one key difference between a jet engine and an automobile engine. If you need/want high HT/HS, an Xw-20 oil will probably not offer it.

 

[stenerson]

Yep, but jet engines use real synthetics. Not that phony groupIII stuff going around nowadays.

 

[ARCOgraphite]

Not an apt comparison.

 

[The_Jeff]

Don't jet engines have roller bearings? They'd be better compared to 2-stroke gas engines which survive on really lousy incidental lube.

And a nit... there's no "10W" @ 100C rating, though it would be a 10-weight.

 

[rogan]

I have heard that F1 engines use straight 5w or 10w so
800 normally aspirated horses at 18000 rpm says it works.

 

[jstutz]

Originally Posted By: rogan
I have heard that F1 engines use straight 5w or 10w so
800 normally aspirated horses at 18000 rpm says it works.


There not trying to hit 200k miles either.

 

[Ayrton]

Originally Posted By: rogan
I have heard that F1 engines use straight 5w or 10w so
800 normally aspirated horses at 18000 rpm says it works.


This is an exceptional point. It may even be straight 0 weight actually. And these days they do approx. 4 races on an engine. They will hit close to 1,000+ intense miles!

 

[SteveSRT8]

Thank you Mr. Senna! J/K.

No way can a plain bearing reciprocating engine be compared to a roller bearing rotating engine.

The stresses aren't there.

 

[Stu_Rock]

Originally Posted By: eljefino
And a nit... there's no "10W" @ 100C rating, though it would be a 10-weight.
This is not correct. In SAE J300, there's no 0, 5, or 10 weight oil. There is 0W, 5W, 10W, 15W, 20W, 25W, 20, 30, 40, 50, and 60.

For the W series, there's only a minimum 100°C KV, not a range. It goes like this:
Code:


0W, 5W 3.8 cSt min

10W 4.1

15W, 20W 5.6

25W 9.3

 

[TallPaul]

I have no problem using a 5w20 if it is Redline which 5w20 has the HTHS of a 30 weight conventional oil.

 

[webfors]

I'm pretty sure my corolla's engine will be fine on 20 weight. If I had a high performance engine (turbo) I'd stick with a syn 30 weight.

The F1 comparison isn't valid. They are trying to squeeze every last bit of power out of the engine due to strict spec requirements, and couldn't care less about getting even 10k out of them.

 

[Panzerman]

I think if you check out the air plane engine oil that actually goes in a "Gas Engine" its pretty thick. Thicker tahn even I would put in a car. A jet engine and car engine are not even apples and oranges, more like watermelons to beach balls.

 

[BBDartCA]

apples and oranges comparison between jet engines and your Ford Taurus

High speed engines can live with thin oil as the EHL film thickness increases and load carrying capability increases as the speed increases. Low RPM high load, use heavy lube.

 

[fdcg27]

The oils used in gas turbines are also expensive esters, and will see neither reciprocating loads nor combustion by-products.
Not a good comparison.

 

[azsynthetic]

Some turbine engines share the same oil with the gear reduction unit so high shear condition does exist. The load-carrying ability of Mobil Jet Oil 254 comes from its synthetic base stock viscosity and, therefore, is not subject to loss from viscosity index additive shear.

 

[Steve S]

There is no way to justify that as a comparison. The lubricating requirments are different.

 

[fsskier]

Just got home from the Indycar Race at Homestead-Miami..... with a paddock pass in hand I was wandering through the garage area...very surprised at the access I was given, virtually ignored as I walked up to the cars.... watched one of the Penske cars get the last checks before being pushed to the track...

OK, Sorry, I did not notice if it was Will Powers car, Castroneves or Ryan Briscoe....
What caught my eye was a dipstick check, followed by cracking the seal on a qt of Mobil 1, and a full qt poured in and the empty pitched in the trash can. Wow, when the car was pushed off to the starting grid I dug the oil bottle out of the trash can... the only oil bottle in there.

Mobil 1 0W40, Series SM, GF-4 oil. Not racing oil or exotica oil, but the same stuff thats at Walmart. I have often heard that specially formulated oils were used here.... usually oils lacking unneeded detergents, dispersant s, cold weather corrosion inhibitors, and probably an extra dose of some ep agents etc but no....

just plain off the shelf Mobil 1.

I suspect that after a few laps at wide open throttle, oil temperatures go up pretty good and the viscosity of the 0W40 is similar to the 0W20 or 0W30 that I usually use....

With all the telemetry coming back, who knows what the oil temps are running in these Indy Cars??

Anyway that was a a thrill.... perhaps exceeded by watching Danica Patrick claw her way up through the pack twice, finally finishing second after a 15 lap side by side dual against Tony Kanaan before squeaking ahead of him.

 

[charbaby]

Just think how cold it is at 35,000 ft at 535mph

 

[ARCOgraphite]

Originally Posted By: fsskier
Just got home from the Indycar Race at Homestead-Miami..... with a paddock pass in hand I was wandering through the garage area...very surprised at the access I was given, virtually ignored as I walked up to the cars.... watched one of the Penske cars get the last checks before being pushed to the track...

OK, Sorry, I did not notice if it was Will Powers car, Castroneves or Ryan Briscoe....
What caught my eye was a dipstick check, followed by cracking the seal on a qt of Mobil 1, and a full qt poured in and the empty pitched in the trash can. Wow, when the car was pushed off to the starting grid I dug the oil bottle out of the trash can... the only oil bottle in there.

Mobil 1 0W40, Series SM, GF-4 oil. Not racing oil or exotica oil, but the same stuff thats at Walmart. I have often heard that specially formulated oils were used here.... usually oils lacking unneeded detergents, dispersant s, cold weather corrosion inhibitors, and probably an extra dose of some ep agents etc but no....

just plain off the shelf Mobil 1.

I suspect that after a few laps at wide open throttle, oil temperatures go up pretty good and the viscosity of the 0W40 is similar to the 0W20 or 0W30 that I usually use....

With all the telemetry coming back, who knows what the oil temps are running in these Indy Cars??

Anyway that was a a thrill.... perhaps exceeded by watching Danica Patrick claw her way up through the pack twice, finally finishing second after a 15 lap side by side dual against Tony Kanaan before squeaking ahead of him.

I wouldnt think an indy car engine would have a dipstick. Mine wouldnt.