If thin oil is so good...

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I know a lot of you are thin oil advocates but I just can't make myself use "water" in my engines no matter what the duty... (0W20 or even 5W20)

If thin oils are so good then why do almost ALL diesel manufacturers still recommend the 15W40 in these engines? Diesels work hard and this thicker Vis oil provides the protection necessary for long engine life, right?

I know diesels and gasoline, apples to oranges but in the crankcase where the oil is, all is the same! Crank, rods and pistons don't care what fuel they burn up top!!

Your thoughts?
 
Last edited:
Unfortunately you're comparing apples to bricks.
wink.gif
 
Originally Posted By: racin4ds
why do almost ALL diesel manufacturers still recommend the 15W40 in these engines?


They don't. All major diesel engine builders now factory fill with 10W-30.
 
The two previous posters on this thread have hit it out of the ball park.

Now go think about your life choices.

End of thread.
 
Originally Posted By: racin4ds
Crank, rods and pistons don't care what fuel they burn up top!!

Your thoughts?


The fuel may not matter, but the size of the bearings relative to power output and rpm as well as the expected usage patterns and expected oil operating temps can all dictate what it needs for oil.

Given the same size bearings, same oil pressure and same oil temps, an engine making 300hp will need thicker oil than the same engine making 200hp, as the stress on the bearings is greater. Let the oil temps run hotter and it'll probably also need thicker oil to keep an adequate film.

Increase power output at low rpm (like a typical diesel compared to many gas engines) and you're also increasing the film strength required to prevent metal contact if you don't change anything else. This is part of why some of the newer turbo gas engines are spec-ing 5W-30 rather than 5W-20 or 0W-20.

In the end, there's no one perfect oil that's correct for every engine.
 
Originally Posted By: racin4ds
I know a lot of you are thin oil advocates but I just can't make myself use "water" in my engines no matter what the duty... (0W20 or even 5W20)

If thin oils are so good then why do almost ALL diesel manufacturers still recommend the 15W40 in these engines? Diesels work hard and this thicker Vis oil provides the protection necessary for long engine life, right?

I know diesels and gasoline, apples to oranges but in the crankcase where the oil is, all is the same! Crank, rods and pistons don't care what fuel they burn up top!!

Your thoughts?
Wait until the CK-4/PC-11 diesel oils come out-you'll really love them! In Canada, they've been using 0W30 for years in their diesels.
 
Originally Posted By: racin4ds
I know a lot of you are thin oil advocates but I just can't make myself use "water" in my engines no matter what the duty... (0W20 or even 5W20)


Looks to me like you're just trying to stir the pot.
 
This viscosity of oil recommended depends on a lot of factors from the quality of the oil to the design and use of the engine to the emission standards and regulations.

If you are dealing with an in warranty engine the only reasonable course is to follow the factory recommendations which happen to be a bit more than just the oil viscosity.

Out of warranty? Have at it. It might just be that a thicker oil of the correct spec's might be a better choice long term use. Is' also possible that either way, you'll never know for sure. There are just too many other variables and you as the only test with no control to resolve the problem.
 
I started the truck up last night at 12*F with a wind gust of 30 mph. I liked the fact I had 5w-20 in it.
According to one oil analyzer few Diesel oils top the charts or even come close in motor oil compared to motor oil designed for gasoline as far as wear reduction is concerned. Of course I have no idea as I didn't do the testing
smile.gif


I switched to 10w-30 Citgard 700 from the OEM 15w-40 fill in several tractors. I liked the results although the oil is not A40 Porsche approved
smile.gif
 
You say 0w20 is 'water' to bearings. Others say 5w40 is like trying to spray 'asphalt' through piston cooler jets and timing chain sprayers.

Each has its application. All the >300k mile Ford Modulars on Xw20 can't be wrong, nor can all the high-mileage engines on Xw40.
 
It still cracks me up that people think their "feelings" matter to an engine as far as lubrication.

An engine is not alive and it is a conglomeration of metal, rubber, and plastic, nothing more.

What's next, someone just can't bring themselves to use gasoline in their gas tank because of the aroma?
 
Not stirring the pot and not some troll, I just can't see the reason behind all the thin oils for nothing other than CAFE/Fuel economy. 5W30 is the absolute thinnest I will run and is in most of my vehicles.

I know diesels are different animals but they work hard, they need excellent protection and they last 2X most gasoline engines. Sure there are other factors here to consider but they don't use thin oil either!!! yes I know some of the newer, light duty stuff specs a 30w but still you don't see no 0W20!!!
 
Hyundai recommends 5W-30 for my diesel engine unless you live down under where they call for 40 wt.

Contrary to popular belief, unless you are having injector spray pastern problems resulting in unburnt fuel leaking past the rings, diesel engine oil will get thicker due to all the soot it has to keep suspended.
 
Great grandpappy used to run SAE50 in the Model T and would change it when he would have to change the bands in the transmission on the hill between Wells and Northville.

If SAE50 was good enough for great grandpappy, goshdarnit, it's good enough for me!
 
Originally Posted By: racin4ds
Not stirring the pot and not some troll, I just can't see the reason behind all the thin oils for nothing other than CAFE/Fuel economy. 5W30 is the absolute thinnest I will run and is in most of my vehicles.

Some companies like Toyota, Honda ... don't sacrifice the hard earn reputations for 0.5 MPG with thinner oil if it does not work well in their engines.

Why Toyota Corolla, Camry and Honda Accord and Civic are the best selling sedan in US for many years ? Are they the best sellers for 0.5 MPG better than competitors ? Or are they the best sellers for reliability ? You know the answer.
 
Originally Posted By: racin4ds
Not stirring the pot and not some troll, I just can't see the reason behind all the thin oils for nothing other than CAFE/Fuel economy. 5W30 is the absolute thinnest I will run and is in most of my vehicles.


Because you know MORE than the people that designed the engine.
 
Originally Posted By: racin4ds
I know diesels are different animals but they work hard, they need excellent protection and they last 2X most gasoline engines. Sure there are other factors here to consider but they don't use thin oil either!!! yes I know some of the newer, light duty stuff specs a 30w but still you don't see no 0W20!!!


They don't spec a 0W-20 for 2 big reasons in my mind:

1: They'd need to make the bearings huge to handle the stress of high torque output at low rpm with the thinner oil, which ends up with a bigger, heavier engine

2: Fleets like commonality. Having half your trucks being able to use 10W-30 or 15W-40 while the other half needs 0W-20 is inconvenient from a maintenance perspective.
 
Originally Posted By: HTSS_TR
Originally Posted By: racin4ds
Not stirring the pot and not some troll, I just can't see the reason behind all the thin oils for nothing other than CAFE/Fuel economy. 5W30 is the absolute thinnest I will run and is in most of my vehicles.

Some companies like Toyota, Honda ... don't sacrifice the hard earn reputations for 0.5 MPG with thinner oil if it does not work well in their engines.

Why Toyota Corolla, Camry and Honda Accord and Civic are the best selling sedan in US for many years ? Are they the best sellers for 0.5 MPG better than competitors ? Or are they the best sellers for reliability ? You know the answer.
they are the best selling because ford made the Oval taurus.
 
Originally Posted By: racin4ds

If thin oils are so good then why do almost ALL diesel manufacturers still recommend the 15W40 in these engines? Diesels work hard and this thicker Vis oil provides the protection necessary for long engine life, right?

I know diesels and gasoline, apples to oranges but in the crankcase where the oil is, all is the same! Crank, rods and pistons don't care what fuel they burn up top!!

Your thoughts?


Can you mention those manufacturers?
I just know about Volvo and they recommend 0W30 A5/B5 in their diesels, Same oil as for their gasoline engines.
 
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