Do single weight oils have a place?

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I saw Jay Leno video where he drove an Areo engined Hispano-Suiza, he said he uses straight 50 wt Lucas engine oil.

The engine is hardly stressed, why not use a multigrade? Starting it on a cold 50 wt seems crazy.
 
Not for me … I have a dozen or so things with gasoline engines and don't see it recommended for any
 
Straight weight oils are good for air cooled engines that are ONLY used in warm and hot ambient temperatures such as air cooled engines on lawn mowers. Mono weight oils are less prone to breaking down to a lighter viscosity by sheering when used in hot air cooled engines.
 
Running 30 in one of my motorcycles which is a shear factory, working well. I decided to use 30 last year in my BMW R65 as the recommended temps fall in my zone. I also changed my breather for about the 10th time, running the hose external and no filter. All good. So I put my 20W-50 synth back in for this summer (actually for winter), and as the bike is used on a lot of gravel, noticed my rear wheel was dirty, like chain lube on the wheel. It's oil coming out the breather. Never happened with the 30.
 
So assuming Jay Leno is being advised by someone knowledgeable, and expence is no real object, has anybody any idea why a 50 wt would be spec'd?

I think think the engine holds about 8 gallons!
 
Originally Posted by 4WD
Not for me … I have a dozen or so things with gasoline engines and don't see it recommended for any



You could likely run a SAE 30 year round where you're at 4wd... But you are too cool for that
lol.gif
 
Grade... not weight.

...and no, I see no reason for it unless you needed an extremely shear stable mineral oil with no VII whatsoever. (IE: Nitro 70)
 
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Originally Posted by sloinker
Air compressors, turbines, gearboxes......

Add Transformers.

I use to use a straight 30..30+ years ago while living in the valley of SoCal. But living up north like I do now, a multi grade is the way to go. I can just stock one lube, a 5w30, and be good year round.

Plus today's engines run hotter and rev higher, so I think the high VI of multi grades are a better fit overall???
 
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I wish I could get a good a good API SN or even SM monograde 30 oil in the UK. My Defender which doesn't get used below freezing and my Mondeo for 9 months of the year would be perfect for one!
 
Originally Posted by expat
So assuming Jay Leno is being advised by someone knowledgeable, and expence is no real object, has anybody any idea why a 50 wt would be spec'd?

I think think the engine holds about 8 gallons!

Comparing vintage piston aircraft engines to modern econobox car engines is apples and donuts. Just what oil do you think he should use? TGMO 0w-20?
 
Originally Posted by expat
I saw Jay Leno video where he drove an Areo engined Hispano-Suiza, he said he uses straight 50 wt Lucas engine oil.

The engine is hardly stressed, why not use a multigrade? Starting it on a cold 50 wt seems crazy.


You do realize that the engine is 1914-design piston pounder, right? And you do realize that aircraft engines of that vintage have significantly different lubrication requirements than a modern day automotive engine, right? And you also understand that Leno has his "garage" in southern California where it's not really all that cold, correct?
 
Originally Posted by Mad_Hatter
Originally Posted by sloinker
Air compressors, turbines, gearboxes......

Add Transformers.

I use to use a straight 30..30+ years ago while living in the valley of SoCal. But living up north like I do now, a multi grade is the way to go. I can just stock one lube, a 5w30, and be good year round.

Plus today's engines run hotter and rev higher, so I think the high VI of multi grades are a better fit overall???


Don't mistake a high VI to mean thermally stable and shear stable. Polyol ester, for example, has great thermal stability at 300+°F, but has a VI of just 70-80. Most straight 30, 40, and 50 grade oils are going to be more thermally stable because they don't contain viscosity modifiers. Same goes for synthetics that can achieve a multi-grade without VII.

Does any of this really matter for a daily commuter that rarely (if ever) sees over 250°F oil temps and 5000+ rpm? Nope.
 
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Guys used to run that honey in their small planes in summer especially if they were burning oil. 50 wt is like slightly diluted STP motor honey. Then along come semi synthetic Aeroshell and Mobile Synthetic. It didn't take long until most switched and never looked back. Avmobile or whatever they called it I avoided as a friend told me he'd seen an engine he'd rebuilt wrecked by sludge. Some years later mobile pulled theirs when someone finally blew the whistle on their sludge making tendency. Not before doing everything on their power to trash the poor wrench who publicly made it known. I read that in Avweb . Aeroshell stated they never could get full synthetic to behave correctly and stayed a blend.
I stuck with Aeroshell as for whatever reason it seemed to burn less than even heavy 30 wt . That was in an 0-200 100hp Continental that ran 🥶cold all the time even summer. The big thing that I learned running an aluminum block engine in the north country was exactly how much everything shrinks and how tight they get when it's cold. You pull the prop through and you can actually feel a significant difference. Heavy Dino av Oil in spite of heating it (30 wt for winter) somewhat took a long time to get where it needed to be. You can just imagine all the metal on metal contact going while that thick pumps Oil up from that tank so far below and it starts doing its job. No wonder those engines need overhauls so often.
Synthetic or semi synthetic in a plane and she seems to behave just like it does in your car, it just lays there on the oil stick. Those older types for whatever reason would actually crawl up the oil stick a half inch or more for whatever reason. They sure did seem stay put on the surfaces a lot better. It could be that's why Leno uses the Dino honey . It's probably better long-term for engine that don't get driven regularly just because of the way it coats and stays on the surfaces.
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Originally Posted by RDY4WAR

Don't mistake a high VI to mean thermally stable and shear stable. Polyol ester, for example, has great thermal stability at 300+°F, but has a VI of just 70-80. Most straight 30, 40, and 50 grade oils are going to be more thermally stable because they don't contain viscosity modifiers. Same goes for synthetics that can achieve a multi-grade without VII.

Does any of this really matter for a daily commuter that rarely (if ever) sees over 250°F oil temps and 5000+ rpm? Nope.

I never mentioned thermal or shear stability.
 
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Originally Posted by Mad_Hatter
Originally Posted by RDY4WAR

Don't mistake a high VI to mean thermally stable and shear stable. Polyol ester, for example, has great thermal stability at 300+°F, but has a VI of just 70-80. Most straight 30, 40, and 50 grade oils are going to be more thermally stable because they don't contain viscosity modifiers. Same goes for synthetics that can achieve a multi-grade without VII.

Does any of this really matter for a daily commuter that rarely (if ever) sees over 250°F oil temps and 5000+ rpm? Nope.

I never mentioned thermal or shear stability.



You said modern engines run hotter and rev higher. That's thermal stability and shear stability.
 
Originally Posted by RDY4WAR
Originally Posted by Mad_Hatter
Originally Posted by RDY4WAR

Don't mistake a high VI to mean thermally stable and shear stable. Polyol ester, for example, has great thermal stability at 300+°F, but has a VI of just 70-80. Most straight 30, 40, and 50 grade oils are going to be more thermally stable because they don't contain viscosity modifiers. Same goes for synthetics that can achieve a multi-grade without VII.

Does any of this really matter for a daily commuter that rarely (if ever) sees over 250°F oil temps and 5000+ rpm? Nope.

I never mentioned thermal or shear stability.



You said modern engines run hotter and rev higher. That's thermal stability and shear stability.

They do run hotter and rev higher and for my OPE where the rpms and heat is fairly constant it makes sense to run a straight grade but I would much rather have a multi vis oil with a VI of 160+ protecting my engine than a mono grade like a Pennzoil sae30 with a VI of 100'ish. The addition of VII's in a multi vis doesn't automatically confer inferior performance. As I'm sure you know that not all VII's are created equal, as is evidenced by lubes that can go 20k miles or more between drains and stay in grade doing it.
 
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