Lubricant Additives

Olefi n Copolymer Viscosity Modifi ers 305

The other API group I blended oils, B2 (Figure 10.18), respond to PPDs in a similar manner to

B1, but only in the SAE 5W-30 formulation. In the 15W-40 case, VM-3 is the only VM to experience

yield stress failure, but only in the presence of PPD-2; all other combinations demonstrate acceptable

pumpability performance.

Figure 10.19 describes the MRV map of B3, the API Group II oil. Overall, low-temperature

viscosities are all quite low for all VM/PPD combinations, although VM-3 again experiences one

yield stress failure in each viscosity grade. VM-1 fails the yield stress criterion once.

Finally, the API Group III SAE 5W-30 formulation (Figure 10.20) was the most diffi cult to pour

depress. All four oils blended with VM-3 were yield stress failures, and each of the other two VMs

showed signifi cant yield stresses for one PPD each.

In summary, the number of MRV failures due to yield stress is given in Table 10.12. Clearly,

one of the LTOCP viscosity modifi ers, VM-3, is substantially more sensitive to PPDs than the other

two polymers. It is especially incompatible with PPD-2. The other LTOCP in this study, VM-2, and

the amorphous VM-1 were found to be far more tolerant of PPD type. Similar to the discussion

in Section 10.5.4.2, one of the major differences between VM-3 and VM-2 is that they were

manufactured by different technologies, broadly described in Figures 10.5 and 10.4, respectively.

10.5.6 FIELD PERFORMANCE DATA

Multigrade lubricants containing EP viscosity modifi ers have been tested in passenger car and

heavy-duty truck engines for over three decades, but very few studies devoted to VM effects on

engine cleanliness and wear have been published. It is generally believed that adding a polymer to

the engine lubricant will have a detrimental effect on engine varnish, sludge, and piston ring-pack

FIGURE 10.20 Rheological results for oil B4. SAE 5W-30.

PPD-1PPD-2

PPD-3 PPD-4

VM-1

VM-2

VM- 3

0

20,000

40,000

60,000

80,000

MRV viscosity (

cP) at -35

°C

YYY

Y Y

Y

TABLE 10.12

Number of MRV Failures due to Yield Stress in Low-

Temperature Viscosity Modifi er/Pour Point Depressant

Interaction Study

VM PPD-1 PPD-2 PPD-3 PPD-4 Total

VM-1 1 1 3 5

VM-2 1 1

VM-3 263213

Total 364619

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