What does Viscosity Index (VI) measure?
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- Опубліковано 3 гру 2020
- Viscosity Index (VI) is one of the fundamental indicators of the suitability of your lubricant for the application. With modern synthetic base oils and viscosity modifier additives, formulators have more control over the viscosity-temperature relationship than ever.
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You saved me sir, my car require full synthetic and
I use my oem oil from dealership always and just realize the vi is 120, barely enough to call it synthetic, what a cheap trick.
Thank you , ill binge all your videos to educate myself
When looking at Penrite oils for example, the viscosity ratings in Cst do not match up with the ratings. For instance a 5w oil is about 15cst at 40c, but according to viscosity charts a 5W should be about about 20 Cst at 40c. The same for 10W and 15W, their ratings seem to be lower than what the classification is supposed to be. Can you explain that at all? In their PAO oils the disparity is even higher. They state a 10W oil which is supposed to be circa 25Cst at 40c but their chart states it is about 15Cst at 40c. It seems their oils are thinner than what they are actually labeled. They have 5W oils which have the same viscosity as 10W oils. It seems labeling or product names are irrelevant. How does this compare with what a manufacturer recommends, if they state a 20W-50 but the 20W50 is actually more like a 5W-30 oil.
I was using some old soviet stuff where cst was quoted at 50 degrees. I used an educated guess.
Please label your graph axies with titles (and units if applicable.)
Thanks for the feedback! This was a pretty early video in the channel. Hopefully I’ve gotten much better at it! 🤞🏽🤞🏽🤞🏽
Very useful thanks,
Glad to help!
Is less saturated base oil better to tolerate more capacity of dissolving dirt & byproducts in the engine pathways???
Good question. Less saturation won’t necessarily dissolve deposits, however the less saturated base oils tend to be less highly refined, and therefore contain more aromatics and sulphur containing molecules. These are more polar and do a decent job of holding deposits in solution. So you are correct, but not because of the saturation.
@@LubricationExplained appreciate your eagerness...top notch educational materials at our hands and the best part, they're free 🤓🤓...thx a lot
I have a question if you could help my it would be great:
I´m trying to see which low viscosity transmission fluid is better. Option A is Pentosin ATF 1 LV with a VI of 168 a Kinematic viscosity at 100ºC of 5.6 mm2/S and 25.3 mm2/s at 40ºC. Option B would be Motorcraft Mercon LV with a VI of 155, a cst @100ºC of 6.0 and a cst @40ºC of 29.6.
From what I could learned from your video I would say Pentosin because it´s VI is higher, but they seem to be very similar, am I right?, can they be interchangeable?
Thanks again for the information.
Tricky question! The world of ATFs is a bit of a minefield because it’s so ingrained with OEM warranties and the spec requirements are a mess. If it helps we did a video on ATFs last week: ua-cam.com/video/OOgzEDpLmmY/v-deo.html
Theoretically a higher VI is great in ATFs because it indicates a higher hydraulic efficiency for the fluid coupling and servos. On the other hand, VI is a combination of base oil quality and VI improver additives. VI improvers tend to shear down over time, so their contribution reduces, whereas base oil VI tends to be more stable. Something else to consider is that Motorcraft is Ford’s private label brand, so if you’re planning on using this ATF in a Ford it might do better from a warranty standpoint.
All to say, it isn’t straightforward. With the publicly available information, you’re correct - the Pentosin product appears to have a higher VI, so if it has approval for your ATF, then it should theoretically be a “better” fluid.
@@LubricationExplained Thanks a lot for your help my car is a Ford. (Lincoln) and is no longer under warranty, right now I'm using Valvoline MAXLIFE that's supposed to be compatible with a lot of transmissions and it's been working ok but wanted to try something different.
I'll watch the recommended video thanks again.
Amazingly explained..
I have a few questions for you.
1. Can you please provide the relation between viscosity Index and Viscosity Grade? Is there any chart, formula or something
2. Also how can we know the actual viscosity by looking at the viscosity grade like what is the viscosity of 5W20?
3. What minerals/chemicals are employed in making these engine oils which makes them operable on cold and hot conditions simultaneously.
Great questions!
1. VI has more to do with the difference between the two grades - so for example a 10W-40 has a lower VI than a 15W-40, so there isn't really an easy way to find an equivalence.
2. The "actual" viscosity will vary by temperature - but the ISO viscosity classification aligns with viscosity at 40C. Here's a link to a site that shows the equivalent ISO viscosity for every SAE grade: www.tribology-abc.com/abc/viscosity.htm
3. Aside from the base oil viscosity index, high temperature properties are generally improved through the use of VI improvers (polymers), while low temperature properties are improved through the use of pour point depressants.
@@LubricationExplained thanks for the response. Concept is very much clear now.
@@LubricationExplainedI don't understand how a 10w40 has a lower viscosity index than a 15w40? Or did you mean viscosity index improver?!
What do you think about the following oils: 1) Honda/Acura synthetic blend 5w-20 which has VI of 159, Kinematic Viscosity at 40°C is 47 and at 100°C is 8.5. 2) Pennzoil Platinum full synthetic (5w-20) which has VI of 167, at 40°C is 45.9 and at 100°C is 8.6. Which would be better overall for my vehicle when doing not more than 5k miles OCI and get better gas mileage?
This is such a difficult thing to make a call one unless you have direct experience of each. Theoretically, a full synthetic will be better from a mileage standpoint thanks to lower traction coefficient.
In your case the 5W20 synthetic blend is semi synthetic blend or a full synthetic oil?. 🤔🤔🤔 Anyhow, I think in your case you arelike trying to split a hair using a razor blade. They are both very similar in their respective properties. Use either oil as long as they are API SN or is not fake oil. For better mileage always kept tire pressure to within +/-0.1barg of stated pressure in hand book and be less aggressive by left foot onto gas pedal. Once a month check engine oil level using dip stick. Then start the engine and wait for rpm to stabilsed. Keep engine running and dip again for engine oil. For my case engine oil level increase by less than 3mm. This should be a good way to verify that the piston rings are having low blowby or that the PCV valve is still ok. Regards.
Change oil and filter every 7500 miles for full synthetic. Some will change every 10,000 to 12,000 miles. n freezing winter try not to exceed engine rpm above 2000 for the 1st 2 miles especially if the coolant temperature, to the radiator, is still below 150 deg F. The reason for the above is that the flowing viscosity of 5w20 engine oil at 0 deg F would be still much thicker than a 10w 40 engine oil at 75 deg F. Regards.
@@whlawson5812 The Honda/Acura oil is synthetic blend(not full). My vehicle is was happy with Pennzoil Ultra Platinum 5w-20 or Acura synthetic blend. Since my comment was posted a year or so ago, I have settled on doing 3k oil changes as after 2k my car starts to consume a bit of oil and by 3k, the dipstick shows 1/4 of oil. So pretty much 3/4 of the quart bottle was consumed. I can add half a quart however it would consume still. Interesting part is that oil level isn't changing first 2k miles and oil is still clean up to that 2k. After that it gets darker more brown(not black). Vehicle has Acura's 3.7L V6 engine J37A2 where Honda introduced some Nikasil liners or some type of coating on the cylinder walls.
@@Charkatak in my car's hand book it basically says: depending on driving condition oil consumption can be up to 0.8litre/1000km. So far it is not more than 0.5litre per 5000km. Engine is year 2006, 1.8 litre supercharged. Car had accumulated anout 130,000 miles. I bought it this June after 3 months of usage. Monthly usage less than 700 miles. Honda engine is reliable. Pay attention on PCV valve for any car more than 6 years old. If it stuck open then it could pull a negative pressure of -0.2barg or less in the engine crankcase during partial throttle load.