Some feel that thicker oil is better. 20w-50 will actually not work as well in the Spyder as the lighter 10w-40 (or 5w-40) oil. Your Spyder will run hotter with 20w-50 and will usually burn more oil too. Sounds counterintuitive, I know. But your oil ring has more trouble squeegee-ing off the thicker oil in a high RPM engine. More oil stays on the cylinder above the piston and it gets burned away. Tends to carbon up your cylinder as well. There are some great articles out there regarding this.
I agree that 10W-40 (or 5W-40) is the oil of choice for our Rotax engines. I was merely trying to find out why someone felt the need to switch to 20W-50. For curiosity's sake.
They don't give you viscosity, they give you the Viscosity Index Number. I'm sure you know that is because viscosity has a spread so one 40 weight oil isn't necessarily going to be the same weight as another 40 weight oil. It's not really as confusing as it may sound.
Think of it as 40 weight, 41 weight, 42 weight through to 50 weight. They don't want to mess with breaking it down that far so any weight oil that is at least 40 and less than 50 is considered 40 weight.
But for testing, you DO want to break things down into finer increments. So they use the Viscosity Index Number instead of the broad 'Viscosity Weight' numbers. So for this oil analysis, you want to compare the original Viscosity Index Number with the tested oil's number. This is a much more accurate way of knowing how much the oil degraded during use.
40 weight oil VIN goes from 12.5 (thinner) to 16.3 (thicker). So as you can see, if the report gave just the viscosity weight it would say 40. But what does that really tell you except that your oil is still within original spec. It won't tell you how much degredation occurred or how close to being out of spec the used oil is.
The original VIN for this oil is 13.8. My test result was 13.3. So I lost .5 VIN in 6,400 miles. The goal here is to stay at or above 12.5 so my reading is very good.
Not quite correct. The Viscosity Index Number is a measurement of how well the viscosity is stable over a temperature range. To quote: "The viscosity index (V.I.) of an oil is a number that indicates the effect of temperature changes on the viscosity of the oil. A low V.I.
signifies a relatively large change of viscosity with changes of temperature.
In other words, the oil becomes extremely thin at high temperatures and extremely thick
at low temperatures. On the other hand, a high V.I. signifies relatively little change in
viscosity over a wide temperature range."
The numbers you are quoting (12.5, 13.3, 13.8, etc) are the actual laboratory-determined viscosities for the oil samples, the units of the number being centistokes (cSt). For the high-temperature viscosity (the "30" or the "40"), the viscosity is measured at 100C or 212F temperature. So on your oil they measured 13.3 cSt at 100C. That is the actual viscosity of your oil at that temperature. Now, where does that actual viscosity fit in the scheme of things? For a "40-weight" oil as defined by SAE and API, the viscosity at 100C must be between 12.6 and 16.3 cSt as you stated. Your oil is still within that range so it is still performing at 40-weight levels. Very good. FYI, I submitted an Amsoil 10W-40 sample after some miles that came back as 12.06 cSt, just below the minimum of the 40-weight range. Still pretty good in my opinion but technically it was now at the top end of the 30-weight range (9.3-12.5 cSt). As for where it started out, Amsoil states that their 10W-40 is typically 13.8 but that doesn't mean every batch leaves their plant with that number. Could be more or less. We should all thank Amsoil for being willing to publish their "typical" numbers. Try to find that out for other oils!
As for VIN, that's something different, as explained above. Now, pure synthetics like Amsoil and Mobil 1 are known to have a high viscosity index, that is they change less with temperature. Lesser-quality oils tend to thin out with temperature and therefore have a lower viscosity at higher temperatures in their native state so the manufacturers add viscosity index improvers to the mix to improve the VIN. With good synthetics, there are fewer, if any, viscosity index improvers added to the mix. Intuitively, the fewer additives the better. At least as far as I'm concerned.
The original Base Number for this oil is 11.1. My test result was 7.40. The goal here is to stay at or above 50% of the original value (which would be just over 5.5) so again, good to go.
The Base Number, or Total Base Number (TBN) is a measure of the additives in the oil that are preventing acid formation and nasty things like that. Again, the 11.1 is "typical" of Amsoil but may not reflect precisely an actual oil that you received. There's no doubt that your 7.40 is a very good reading, however. In the sample I referenced above, my TBN had gone down to 6.1, still very good. Again, I thank Amsoil for giving us an idea ("typical") of where we started out, 11.1 in this case.
Bottom line -- I, too, was very pleased with my Amsoil test results. My sample was run at a different lab than you used and one that is not associated in any way with Amsoil. But we both got good results and that's what counts!
Is everyone awake??
