Even the best - shear stable - PAO and/or Ester based synthetics will thicken very slowly due to oxidation/evaporation, over the course of an extended drain interval of > 15,000 miles. The best performance I've seen is a 2% increase in viscosity for every 1000 miles; starting at the point when the oil has been in use for 10,000 miles. So you can roughly expect this type of behavior, if you track viscosity as a function of miles:
Miles on sample ....Viscosity Increase @ 100C/210F:
10,000...viscosity unchanged or slightly thinner
15,000 ...+10%
20,000...+20%
25,000...+30%
30,000...+40%
35,000...+50%
For example, if you run the Series 2000 formulation for 35k miles, it will thicken up by approx 50% at both low and high temps, under ideal conditions. At subzero temps, the "CCS" viscosity will increase from a 0wt to a 5wt. The high temp viscosity @ 100C will normally end up in the 15-18 Centistoke range. In laymans terms, the viscosity will increase from an SAE 0w-30 to a 5w-40, or "thin" 5w-50 - either of which is perfectly acceptable in terms of protection and performance.
The key to maintaining excellent wear protection over very long drain intervals is to make sure the oil still flows well on startup/warmup, even in temps well below 0F. Allowing the oil to very slowly thicken by a grade at operating temp will cause fuel efficiency to drop by 1%-3% towards the latter part of the drain interval, but won't cause any function problems.
Those of you who follow the European oil scene may have noted that many of the new long drain, ACEA "A5/B5" and VW 503/506 spec oils are SAE 0w-30 grades. Now you know the reasoning that went into that viscosity selection, particularly for gas engines. The popular TDI diesel engines produce much less oxidative thickening of the oil, however you also have soot related thickening to contend with in those applications.
Tooslick
www.lubedealer.com/Dixie_Synthetics
[ November 17, 2003, 09:21 AM: Message edited by: TooSlick ]
Miles on sample ....Viscosity Increase @ 100C/210F:
10,000...viscosity unchanged or slightly thinner
15,000 ...+10%
20,000...+20%
25,000...+30%
30,000...+40%
35,000...+50%
For example, if you run the Series 2000 formulation for 35k miles, it will thicken up by approx 50% at both low and high temps, under ideal conditions. At subzero temps, the "CCS" viscosity will increase from a 0wt to a 5wt. The high temp viscosity @ 100C will normally end up in the 15-18 Centistoke range. In laymans terms, the viscosity will increase from an SAE 0w-30 to a 5w-40, or "thin" 5w-50 - either of which is perfectly acceptable in terms of protection and performance.
The key to maintaining excellent wear protection over very long drain intervals is to make sure the oil still flows well on startup/warmup, even in temps well below 0F. Allowing the oil to very slowly thicken by a grade at operating temp will cause fuel efficiency to drop by 1%-3% towards the latter part of the drain interval, but won't cause any function problems.
Those of you who follow the European oil scene may have noted that many of the new long drain, ACEA "A5/B5" and VW 503/506 spec oils are SAE 0w-30 grades. Now you know the reasoning that went into that viscosity selection, particularly for gas engines. The popular TDI diesel engines produce much less oxidative thickening of the oil, however you also have soot related thickening to contend with in those applications.
Tooslick
www.lubedealer.com/Dixie_Synthetics
[ November 17, 2003, 09:21 AM: Message edited by: TooSlick ]
