TractorByNet.com - View Single Post - 10-30W versus 10-40W

Doc_Bob · 05-12-2008, 02:29 PM

"SAE 30 is SAE 30 no matter what the "W" prefix number is: 0W, 5W or 10W. This viscosity in centistokes (cSt) @ 100 degrees C is with the minimum of 9.3 cSt and a maximum of 12.5 cSt.

"SAE 40 is SAE 40 no matter what the "W" prefix number is: 5W, 10W, 15W or 20W. The viscosity @ 100 degrees C is within the minim of 12.5 cSt and a maximum of 16.3 cSt.

"SAE 50 is SAE 50 no matter what the "W" prefix number is: 5W, 10W, 15W or 25W. The viscosity @ 100 degrees C is within the minimum of 16.3 cSt and a maximum of 21.9 cSt.

So cSt is the "key".

30 weight has min 9.3 and max 12.5 at 100 degrees C

40 weight has min 12.5 and max 16.3 cSt at 100 degrees C.

So, technically, 40 W can fall in the range for 30W at 100 degrees C. with a cSt 12.5.

05-12-2008, 02:29 PM	#3 (permalink)
Doc_Bob Elite Member Join Date: Mar 2006 Location: Wisconsin Posts: 2,701	Re: 10-30W versus 10-40W "SAE 30 is SAE 30 no matter what the "W" prefix number is: 0W, 5W or 10W. This viscosity in centistokes (cSt) @ 100 degrees C is with the minimum of 9.3 cSt and a maximum of 12.5 cSt. "SAE 40 is SAE 40 no matter what the "W" prefix number is: 5W, 10W, 15W or 20W. The viscosity @ 100 degrees C is within the minim of 12.5 cSt and a maximum of 16.3 cSt. "SAE 50 is SAE 50 no matter what the "W" prefix number is: 5W, 10W, 15W or 25W. The viscosity @ 100 degrees C is within the minimum of 16.3 cSt and a maximum of 21.9 cSt. So cSt is the "key". 30 weight has min 9.3 and max 12.5 at 100 degrees C 40 weight has min 12.5 and max 16.3 cSt at 100 degrees C. So, technically, 40 W can fall in the range for 30W at 100 degrees C. with a cSt 12.5.