How Thin Can it go ?

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Oil is getting expensive. I'm thinking about cutting it 50/50 with some cheap mazzola oil that I picked up on sale for 99 cents a gallon. That's the thinnest I'll go in America. When I go to Europe I'll stick with 5w40 because it's not America.
 
Originally Posted By: LubeLuke
Originally Posted By: bigdreama
Originally Posted By: virginoil

In Australia 5w-30 any thinner than this is pointless and a futile exercise due to our climatic conditions.


Why would you say that? I'm in Florida and the engine in my car runs at the same temp regardless of outside conditions because it is liquid cooled and has a thermostat.


Your coolant fans and thermostat control the temperature of your coolant, not necessarily the internal engine components or oil.
Unless you have a heat exchanger for your oil then the oil is cooled through the sump and filter mainly. Outside air temperature plays a big factor here.
Also consider the intake temperature. Now you have a different combustion mixture and timing. Your exhaust gas temperatures are different. So is your turbo coolant or only oil cooled?
Your crankshaft is oil cooled. So are the rod bearings. Are your main bearings cooled by the block and coolant or oil? Probably both.


Have been playing, sticking a type K thermocouple down the dipstick tube in my supercharged V-6 after driving...so the T/c is right where the oil is draining down from the crank.

Normal oil temperature after my 25km commute is 105-110C, but if I hold it in 2 for the last 10km, raising the revs from 1,800 to 4,000RPM, same road speed, and tractive load, I can pull 130-135C.

(Same cooling system)
 
Shannow: Normal oil temperature after my 25km commute is 105-110C, but if I hold it in 2 for the last 10km, raising the revs from 1,800 to 4,000RPM, same road speed, and tractive load, I can pull 130-135C.

SR5: Thanks for taking a direct measurement and posting the results.
 
Originally Posted By: SR5
Shannow: Normal oil temperature after my 25km commute is 105-110C, but if I hold it in 2 for the last 10km, raising the revs from 1,800 to 4,000RPM, same road speed, and tractive load, I can pull 130-135C.

SR5: Thanks for taking a direct measurement and posting the results.


0C this morning it only got to 95C...coldest I've ever seen it after the 25km trip.
 
I tried switching my gauges to F, mph, psi and gallons. That lasted about an hour.

Question; Does the oil cool or heat the crankshaft and big end rod bearings?
 
Originally Posted By: used_0il
I tried switching my gauges to F, mph, psi and gallons. That lasted about an hour.

Question; Does the oil cool or heat the crankshaft and big end rod bearings?


Crankshaft, the oil drag within certainly heats the shells.

Big end, I'm positive the oil is the major contributor to bearing heat also.
 
Originally Posted By: mjoekingz28
Yes, but a jet spins like a turbocharger-unlike a reciprocating piston.


Cujet- I am assuming turbojets can spin higher rpms than a turbofan, but what is a ballpark rpm?

Does altitude change this number?


The big difference being the piston/ring/cylinder situation. Gas turbine engines have gears, bearings and drives that need robust lubrication.

The main gas producer section of the turbine engines on our helicopter often spins over 50,000 RPM, 100% = 54,117. And, yes, it spins far faster at altitude than at sea level. Might be 94% at sea level.

The power turbine runs at a fixed speed, 44,038 RPM, directly geared to the rotor system, which is always at 100% (385 RPM)

So that thin BP2380 oil takes a high RPM engine and lubricates it and all of the parts necessary to reduce it to very high torque, very high load (all flight loads) conditions.

Interestingly, the engine output shaft is 6000 RPM, and the starter/generator RPM is 12,334.

Oil pressure hovers above 60PSI and can go over 200PSI on cold starts.
 
Originally Posted By: LubeLuke
Your crankshaft is oil cooled. So are the rod bearings.


Crank is actually oil heated...there's no conductive path to the crankshaft bar through the oil, and in reality the heat that's in the crank has a fair bit to do with the viscous drag of the oil.
 
Originally Posted By: Merkava_4
Originally Posted By: expat
But is thinner really better?


No it's not, viscosity is an important part of lubrication.


Yes, but unless a blender releases a bad batch, all engine oil has viscosity. As long as it's for an engine "it" will always have viscosity.

I have been thinking about that for a couple of weeks I guess.
 
Hi,
Mrjhynx - In the end the engine's operating viscosity will be driven by the minimum HTHS viscosity allowed within an engine family. Emerging additives, metallurgy and coatings will all play a part

It is possible I suspect to have say a 0W-10 (why?) but with a HTHS viscosity of perhaps around 3>. Again it will be an overall cost/benefit exercise driven by environmental concerns, emerging technologies and energy consumption within the Global family

This has been the case for several decades in Euro design - and Euro designs now heavily influence the USA's engine mix
 
Originally Posted By: Cujet
Gas turbine engine and highly loaded helicopter transmissions use extremely thin oil. These engines and components last a very, very long time. Wear is generally not an issue.

Kinematic: 24.2 mm2/s (24.2 cSt) at 40°C

Kinematic: 4.97 mm2/s (4.97 cSt) at 100°C

I'd suspect that as design and materials change, the thin oils will perform extremely well.
What is the quality of the metals used ? Expensive would call aircraft parts expensive.
 
The turbines do have the benefit of better materials $$$ as CT8 points out and their continous motion in one direction without power pulses is also advantageous. Similarly the transmissions are under a fairly steady, albeit heavy load so there is little comparable accel/decel for the system to deal with. Metal detectors still figure prominently in the trannys for obvious reasons. The care of design and build of turbines with superb materials makes them things of beauty. Wish we could use them in cars.
 
Originally Posted By: Shannow
aquariuscsm,
every answer depends on the question that's asked.

...the turbine OEMs offer ISO46 and ISO32 as options (just over 5 to just under 7 cst at 100C respectively)...the latter offers a greater safety margin "headroom", industry usually chooses the ISO32 on a risk/reward in terms of an infinitesimal but real improvement in efficiency over a 25 year life.

Other applications can't survive for any length of time on something less than ISO320 (25cst@100C, and that's thick), some other small group ISO1000, 55cst at 100C).




Since when ISO viscosities are measured at 100C. Nope, they're not. ISO is taken at 40C.
 
Pontual is correct.

ISO viscosity grade is pegged at 40 C only , unlike API.

However Shannow is also not incorrect , for he says:

ISO 32's viscosity is 5ish cSt at 100C; and ISO 46's viscosity is 7ish at 100C.
 
Last edited:
Originally Posted By: Pontual
Originally Posted By: Shannow
aquariuscsm,
every answer depends on the question that's asked.

...the turbine OEMs offer ISO46 and ISO32 as options (just over 5 to just under 7 cst at 100C respectively)...the latter offers a greater safety margin "headroom", industry usually chooses the ISO32 on a risk/reward in terms of an infinitesimal but real improvement in efficiency over a 25 year life.

Other applications can't survive for any length of time on something less than ISO320 (25cst@100C, and that's thick), some other small group ISO1000, 55cst at 100C).




Since when ISO viscosities are measured at 100C. Nope, they're not. ISO is taken at 40C.


Did I CLAIM that they were measured at 100C ?

NO, i stated what their operational viscosities TYPICALLY are at 100 for the ISO viscosities listed, and that turbine users typically pick the tiny margin in efficiency of an ISO32 over a 46 at a tiny reduction in film thickness.

Am I to read your claim as being that ISO viscosities are only to be used at 40C ?
 
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