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The low end kinematic viscosity of a SAE 40 wt oil at 100C is 12.5 cSt. Under 12.5 is a SAE 30 wt. So you are right on the border.

Is it possible that you didn't maintain the same viscosity when you switched to the Delo 400LE? It appears that the first sample may be a 15w-40. The second and third samples look like maybe a 10w-30?
 

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Discussion Starter #22
The low end kinematic viscosity of a SAE 40 wt oil at 100C is 12.5 cSt. Under 12.5 is a SAE 30 wt. So you are right on the border.

Is it possible that you didn't maintain the same viscosity when you switched to the Delo 400LE? It appears that the first sample may be a 15w-40. The second and third samples look like maybe a 10w-30?
The first sample was the old formulation Delo 15w-40 multigrade, the next two samples are Delo15w-40LE
 

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The first sample was the old formulation Delo 15w-40 multigrade, the next two samples are Delo15w-40LE
The sample looks good to me... @ 12.55 cSt and 12.63 cSt the oil is still in grade. I would not worry about it at all.

And, the rest of the sample looks good too!
 

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I should also point out that the correct way to perform oil analysis is to first send in a unused sample to develop a baseline. The base line viscosity of the two different oils that you are using may be different.

If I didn't know that you had changed oil between the first and second samples, it would appear that there may be a problem with viscosity of the second and third sample because they are different than the first sample.

When you examine samples you are looking not only at the minimum and maximum values but also at changes that are inconsistent with previous samples. In our case where we are doing a fleet, we also look closely at samples that are inconstant between like vehicles or components.

My guess is that the next sample, if you continue to use the Delo15w-40LE, will be the similar to sample two and three with the viscosity being on the low end of the grade. I would not be a bit afraid of using the Delo15w-40LE and seeing the viscosity values that you are looking at. If you want get a more complete picture, you could always send in a unused sample of the oil that you are using to establish a baseline.
 

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I don't see any glaring problems with that oil sample.
Wear metals look very good, if anything the viscosity could improve your fuel mileage slightly.
 

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Discussion Starter #26
I should also point out that the correct way to perform oil analysis is to first send in a unused sample to develop a baseline. The base line viscosity of the two different oils that you are using may be different.

If I didn't know that you had changed oil between the first and second samples, it would appear that there may be a problem with viscosity of the second and third sample because they are different than the first sample.

When you examine samples you are looking not only at the minimum and maximum values but also at changes that are inconsistent with previous samples. In our case where we are doing a fleet, we also look closely at samples that are inconstant between like vehicles or components.

My guess is that the next sample, if you continue to use the Delo15w-40LE, will be the similar to sample two and three with the viscosity being on the low end of the grade. I would not be a bit afraid of using the Delo15w-40LE and seeing the viscosity values that you are looking at. If you want get a more complete picture, you could always send in a unused sample of the oil that you are using to establish a baseline.[/QUO


Thanks for looking. I like the idea of sending in a unused sample.
I guess I was just being a little too picky with seeing the viscosity on the low end of the scale I wondered if I should switch to a different brand to improve.
 

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I wouldn't worry at all. Its in grade and I am pretty sure your baseline will show degradation is not a problem.

Another reason to establish a baseline is to monitor silicone (dirt). The threshold for the warning level is generally 10ppm above the baseline. With 15ppm above the baseline being critical. This is important to monitor if you are using an aftermarket air filter because often they do not filter as well as the stock filter.

Because you change your oil at essentially half the recommended interval, I would expect the oil to only have collected half of the silicone that would be present at the full change interval. I would have some concern if I was above half the threshold value in 3500 miles.
 

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These engines don't have any trouble running a 10w-30. I wouldn't hesitate to run that oil out farther and see if the viscosity keeps dropping, I bet it levels out right around 12 which puts it right in the 30 weight range. Right now it's just on the edge of what a 40 would be.
 

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