Synthetic oil or not?
- Thread starter Rickcin
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Me too... it was just to reinforce the importance of the letter "W" in the SAE classification, but it doesn't mean that it didn't exist, doesn't exist or that it won't be created in the future... it's just a question of market or industry needs.
For example: why have SAE 0W30, SAE 5W30, SAE 10W30 and SAE 15W30 oil? All have the same viscosity and SAE 0W30 covers all other temperature ranges.
There must be a reason, but it is not explicit for us laymen.
Still going with 30w oil. I grew up on it. And darn it, I'm old and I will get my way LOL LOL.
Besides SAE is not a spec like W is. Just a group of guys like I already said. They makes the specs. What ever........ Thread closed.
slomo
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Isn't the first number viscocity at a certain cold temp, for easier start ups?
In a multi grade oil, say 5w-30, the 5 is the grade of the oil. It's a 5 grade oil ALL THE TIME (thin). BUT it has viscosity improvers that make it thick as a 30 grade at 212F or 100C (same thing). So it pours easy when cold and has a 30 grade thickness when hot at 212F again.
So knowing this, multi-grade oils SHEAR DOWN way faster than a straight grade will every time. It's an oil trying to do double duty, perform at hot and cold temps. Things like water or air cooled, oil running through gears or a transmission all effect shear rates. Like in a motorcycle, that oil will shear down to a 5w-20 or 5w-10 in a few months if ridden hard.
Back to mower engines, SAE 30 is the perfect tool for the job. Mower engines reach full smoking hot temps in roughly 60 seconds. You want that thick film protection right away. Most people mow in over 60f temps so it performs okay at startup. Single grade oils are doing ONE job, perform at high temps. Shearing is way less than a 5w-30 oil. Briggs and Kawi know this. Briggs says that a full syn 5w-30 will use more oil and needs to be checked often.
There's more to it like molecule sizes and so on.
slomo
At cold temps being 32f or 0C, the first number is the cold viscosity rating. Smaller first number the easier it pours when cold.
slomo
No...SAE is an old world society and with strong accreditation, 99.99% of oil manufacturers carry their certificate.Still going with 30w oil. I grew up on it. And darn it, I'm old and I will get my way LOL LOL.
Besides SAE is not a spec like W is. Just a group of guys like I already said. They makes the specs. What ever........ Thread closed.
slomo
The letter W (in the SAE specification) is indicative of oils for negative temperature ranges in °C, partial or total.
I searched for 30W oils and I only found one from West Marine, but it has the SAE 30 seal (-5 to + 35°C) and it seems to me to be the only one that although it works in a small range below zero, SAE does not put the letter W in the specification... must be really to confuse...
Sorry, but there is a misconception here...In a multi grade oil, say 5w-30, the 5 is the grade of the oil. It's a 5 grade oil ALL THE TIME (thin). BUT it has viscosity improvers that make it thick as a 30 grade at 212F or 100C (same thing). So it pours easy when cold and has a 30 grade thickness when hot at 212F again.
So knowing this, multi-grade oils SHEAR DOWN way faster than a straight grade will every time. It's an oil trying to do double duty, perform at hot and cold temps. Things like water or air cooled, oil running through gears or a transmission all effect shear rates. Like in a motorcycle, that oil will shear down to a 5w-20 or 5w-10 in a few months if ridden hard.
Back to mower engines, SAE 30 is the perfect tool for the job. Mower engines reach full smoking hot temps in roughly 60 seconds. You want that thick film protection right away. Most people mow in over 60f temps so it performs okay at startup. Single grade oils are doing ONE job, perform at high temps. Shearing is way less than a 5w-30 oil. Briggs and Kawi know this. Briggs says that a full syn 5w-30 will use more oil and needs to be checked often.
There's more to it like molecule sizes and so on.
slomo
Every oil undergoes a change in viscosity due to heat, that is, the higher the heat, the lower its viscosity... the graph below demonstrates this and more...
Credits: https://www.kewengineering.co.uk/Auto_oils/oil_viscosity_explained.htm
On the vertical axis, we have the effective viscosity (the SAE indication is more referenced to positive temperature and does not actually express the viscosity value) of 4 types of oil.
And horizontal axis is temperature in °C.
All 4 types have high viscosity values when cold (close to zero) and decreasing values as the oil is heated, all reaching less than 20 cSt (Centistokes) when at 100°C.
For those who don't know, the density of water is 1,003 Centistokes (cSt), that is, at 100°C the oil practically turns into water.
But the working temperatures of each oil are much lower, where each still contains a viscosity value that satisfies the engine's need.
The graph also demonstrates why 5W30 oil is better than 10W30 at a temperature close to zero, as it is less viscous and this facilitates engine starts... It also explains, by deduction, why all engines must be temperature-controlled or limited.
As for the use of SAE 30 (or 30W), for all mowers I believe that it would not be correct with temperatures there ranging from -20 to +40°C (all over the country), as although it is unlikely to cut grass below zero, you use implements to remove snow or transport objects inside the farm.
The right thing is to adjust the oil according to the temperature of the working region... the 30W is good, but it doesn't produce a miracle...
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bullet bob
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Just gotta love a good 'ole oil thread.........