A Comparison of Iron Wear Levels Using BITOG Reported UOAs
By OldCowboy
The first 60 pages of 20 weight and 30 weight UOAs have been compiled into a spreadsheet database. This is too much data to present in a forum topic, but the data will be provided to anyone who sends me a PM.
The following criteria were used to determine if a UOA was excluded:
- Samples with unit mileage less than 20,000 were not included based on the assumption that they may still be showing high wear levels due to ongoing break-in.
- Samples with additives (MMO, Auto-RX, etc.) were not included due to unknown effects of the additive.
- Samples with make-up oil were not included. This is because I had no way of knowing what effect the addition of make-up oil had with regard to the wear metals.
- There is only one sample included per OP/engine/oil combination to ensure the data were not skewed by multiple nearly-identical samples.
- Samples that did not have iron as the highest wear metal were not considered unless the UOA indicated that this was a normal condition for that particular type engine.
- Samples that had significant fuel or water contamination were not considered due to higher than normal wear to be expected from these samples.
- Samples with less than 2000 miles on the sample were not included.
- Samples which did not have the engine identified and could not be determined via Internet search were not included. This occurred when a model had multiple engines available.
At this time there are 245 samples in this database.
- 112 samples from 4 cylinder engines (34 w/ 20 wt and 78 w/ 30 wt)
- 87 samples from 6 cylinder engines (22 w/ 20 wt and 65 w/ 30 wt)
- 46 samples from 8 cylinder engines (17 w/ 20 wt and 29 w/30 wt)
The database contains the following data fields:
Motor Oil & Viscosity
Wear Metals (Fe, Cr, Ni, Al, Cu, Pb, Sn), normalized to ppm/1000 miles
Original Poster of the UOA
Date the UOA was posted
Engine Make and Displacement
Oil Mileage
Unit Mileage
It has been stated in many documents/references that iron is the only wear metal which consistently increases as mileage increases. Therefore, this white paper will only focus on iron wear levels.
4 CYLINDER ENGINES
20 Weight vs. 30 Weight - Iron ppm per 1000 miles
Code:
20 Weight 30 Weight
Minimum Value 0.50 0.44
Maximum Value 3.24 4.76
Average Value 1.48 1.61
Standard Deviation 0.71 0.96
95% Confidence Value 0.50 0.21
95% Confidence Interval 0.98-1.98 1.40-1.81
Number of Samples 34 78
The 30 weight oils had a larger spread in iron wear levels (0.44 - 4.76 vs. 0.50 - 3.28) and a slightly higher average value (1.61 vs 1.48). However the 95% confidence value for the 30 weight oils was smaller (0.21 vs 0.50), mainly due to the larger sample size. It should be noted that the mix of engines in both the 20 weight and 30 weight UOAs was very similar.
The 95% Confidence Intervals for the 20 weight samples and 30 weight samples overlap. Thus, there is probably no statistically significant differences in the iron wear levels between 20 weight and 30 weight oils in the 4 cylinder engines reported in these UOAs. A student'sT-test run on this data indicated that the iron wear levels between the 20 weight and 30 weight oils were NOT statistically different at the alpha = 0.05 level.
Differences Among 20 Weight Oils
There were some noticeable differences in iron wear levels between the various 20 weight oils reported in these UOAs. However, many of the oils were only represented by two or three sample reports. It was arbitrarily decided to only perform statistical comparisons on oils that had five or more sample reports.
Among the 20 weight oils, only two oils had five or more samples reported. These were Amsoil and Mobil 1. The statistical data associated with these two oils are shown here:
Code:
Amsoil 20 Mobil 1 20
Minimum Value 0.50 1.02
Maximum Value 1.80 3.10
Average Value 1.10 1.81
Standard Deviation 0.52 0.70
95% Confidence Value 0.42 0.49
95% Confidence Interval 0.68-1.52 1.32-2.30
Number of Samples 6 8
There is only a slight overlap of the 95% Confidence Interval between these two oils, so a student's T-test comparing the two sample groups was conducted. According to the T-test, there was a statistically significant difference between the two sample groups with an alpha value of 0.05. Thus, it can be said that the Mobil 1 20 weight sample group shows more iron than the Amsoil 20 weight sample group with a confidence of 95%.
Differences Among 30 Weight Oils
Five oils in the 30 weight oil group had five or more UOAs reported. The summarized data is presented below:
Code:
Amsoil Castrol Edge Castrol Syntec
Minimum Value 0.59 0.73 0.67
Maximum Value 4.37 2.95 2.77
Average Value 1.80 1.56 1.72
Standard Deviation 1.15 0.88 0.80
95% Confidence Value 0.75 0.71 0.64
95% Confidence Interval 1.04-2.55 0.85-2.26 1.08-2.36
Number of Samples 9 6 6
Mobil 1 Pennzoil Platinum
Minimum Value 1.15 0.44
Maximum Value 4.39 3.67
Average Value 2.32 1.28
Standard Deviation 1.08 0.91
95% Confidence Value 0.64 0.56
95% Confidence Interval 1.68-2.96 0.71-1.84
Number of Samples 11 10
There is significant overlap in the 95% Confidence Intervals of all of these sample groups. However, there is the least overlap between Mobil 1 and Pennzoil Platinum. A student's T-test shows that the Mobil 1 sample group shows higher iron wear levels than the Pennzoil Platinum sample group at an alpha of 0.03. This is a statistical significance at the 97% level. None of the other sample groups showed a significant difference as compared to Pennzoil Platinum. Additionally, none of the other sample groups showed a significant difference as compared to Mobil 1.
The 30 weight sample groups can be ranked in the following order, from lowest to highest iron wear levels:
Pennzoil Platinum < Castrol Edge < Castrol Syntec < Amsoil
Comparison of Amsoil and Mobil 1 20 weight vs 30 weight
Since both Amsoil and Mobil 1 had appropriately large sample groups in both 20 weight and 30 weight viscosities, the obvious question is which viscosity produces the least iron wear. This comparison is shown below:
Code:
Amsoil 20 Amsoil 30
Minimum Value 0.50 0.59
Maximum Value 1.80 4.37
Average Value 1.10 1.80
Standard Deviation 0.52 1.15
95% Confidence Value 0.42 0.75
95% Confidence Interval 0.68-1.52 1.04-2.55
Number of Samples 6 9
Mobil 1 20 Mobil 1 30
Minimum Value 1.02 1.15
Maximum Value 3.10 4.39
Average Value 1.81 2.32
Standard Deviation 0.70 1.08
95% Confidence Value 0.49 0.64
95% Confidence Interval 1.32-2.30 1.68-2.96
Number of Samples 8 11
Both oils show lower average wear levels in the 20 weight sample group than the 30 weight sample group. A student's T-test shows that neither of these 20 weight oils is statistically different than their 30 weight counterpart at an alpha = 0.05 level.
6 CYLINDER ENGINES
20 Weight vs. 30 Weight - Iron ppm per 1000 miles
Code:
20 Weight 30 Weight
Minimum Value 0.60 0.61
Maximum Value 6.57 19.02
Average Value 1.82 2.72
Standard Deviation 1.20 3.00
95% Confidence Value 0.76 0.66
95% Confidence Interval 1.06-2.59 2.06-3.38
Number of Samples 22 78
The 20 weight sample group had significantly lower iron levels as measured by a student's T-test at an alpha = 0.05 level. The mix of engines in the 30 weight sample group differed from the 20 weight group in that the 30 weight group had engines from GM and Chrysler that were not present in the 20 weight group. These engines tended to have higher iron levels than the Ford, Honda, Mitsubishi, Hyundai, Kia, Toyota, and GM 3.6L engines in the 20 weight group. Therefore, I stripped all Chrysler and non-3.6L GM engines out of the 6-cylinder 30 weight sample group and reexamined the 20 vs 30 weight question with these results:
Code:
20 Weight 30 Weight
Minimum Value 0.60 0.62
Maximum Value 6.57 11.83
Average Value 1.82 2.15
Standard Deviation 1.20 1.95
95% Confidence Value 0.50 0.56
95% Confidence Interval 1.32-2.32 1.58-2.71
Number of Samples 22 46
When the Chrysler and non-3.6L GM engines are removed from the 30 weight samples, there is no significant difference between the 20 weight and 30 weight oils. This adjusted 30 weight sample group will be used for the remaining 6 cylinder statistical comparisons. It should be noted that both the range of values and the average value dropped when Chrysler and non-3.6L GM 6 cylinder engines were removed from the sample group.
Differences Among 30 Weight Oils
Only three 30 weight oils had the requisite number of samples for statistical comparison; Mobil 1, Pennzoil Platinum, and Pennzoil Ultra:
Code:
Mobil 1 Penn Plat Penn Ultra
Minimum Value 0.62 0.89 0.79
Maximum Value 8.00 3.69 3.66
Average Value 3.01 1.44 1.59
Standard Deviation 2.80 0.93 1.18
95% Confidence Value 2.24 0.64 1.03
95% Confidence Interval 0.77-5.25 0.80-2.08 0.56-2.62
Number of Samples 6 8 5
Given the major overlap in the 95% Confidence Intervals of the three sample groups, it comes as no surprise that student's T-tests comparing the three sample groups shows no significant differences.
Comparison of Pennzoil Platinum 20 weight vs 30 weight
Pennzoil Platinum is the only oil with enough samples in both viscosities to allow a statistical comparison:
Code:
Penn Plat 20 Penn Plat 30
Minimum Value 1.12 0.89
Maximum Value 2.20 3.69
Average Value 1.53 1.44
Standard Deviation 0.39 0.93
95% Confidence Value 0.31 0.64
95% Confidence Interval 1.22-1.84 0.80-2.08
Number of Samples 6 8
Because the 95% Confidence Interval for the 20 weight Pennzoil Platinum samples is totally contained within the 95% Confidence Interval for the 30 weight Pennzoil Platinum samples, there is no significant difference between the iron wear levels of these two oils.
8 CYLINDER ENGINES
20 Weight vs. 30 Weight - Iron ppm per 1000 miles
Code:
20 Weight 30 Weight
Minimum Value 0.63 0.65
Maximum Value 7.00 7.60
Average Value 2.45 2.73
Standard Deviation 1.66 1.98
95% Confidence Value 0.79 0.72
95% Confidence Interval 1.66-3.24 2.01-3.45
Number of Samples 17 29
The 8 cylinder 20 weight sample group consisted of engines from Ford and Chrysler. The 8 cylinder 30 weight sample group consisted of engines from Ford, Chrysler, Toyota, GM, and Nissan.
Both the overlap of the 95% Confidence Intervals and a student's T-test show that there is no significant difference between the 20 weight samples and the 30 weight samples.
Comparison of Amsoil and Mobil 1 30 weight
The only oils which had enough samples to compare were the Amsoil 30 weight and the Mobil 1 EP 30 weight:
Code:
Amsoil 30 Mobil 1 EP 30
Minimum Value 0.65 0.76
Maximum Value 5.00 6.73
Average Value 2.35 3.31
Standard Deviation 1.52 2.94
95% Confidence Value 1.21 2.57
95% Confidence Interval 1.14-3.56 0.74-5.88
Number of Samples 6 5
Both the overlap of the 95% Confidence Intervals and a student's T-test show that there is no significant difference between the Amsoil 30 weight samples and the Mobil 1 EP 30 weight samples.
Comparison of 20 weight vs 30 weight oils - Ford and Chrysler V8 Engines
Because the 30 weight group had a different mix of engines than the 20 weight group, the Toyota, GM, and Nissan engines were removed from the 30 weight group and the comparison was repeated:
Code:
20 Weight 30 Weight
Minimum Value 0.63 2.00
Maximum Value 7.00 7.60
Average Value 2.45 4.25
Standard Deviation 1.66 2.09
95% Confidence Value 0.79 1.37
95% Confidence Interval 1.66-3.24 2.88-5.61
Number of Samples 17 9
When Ford and Chrysler V8 engines are compared using 20 weight vs 30 weight oils, the 20 weight sample group showed lower iron levels at the alpha = 0.04 level. This is a 96% significance level. It should be noted that the average iron wear value increased when the Japanese and German V8 engines were removed from the sample group.
GENERAL OBSERVATIONS
- 20 weight oils consistently showed lower average iron levels than 30 weight oils. The only time this difference was statistically significant was with Ford and Chrysler V8 engines.
- Mobil 1 oils tend to show higher iron wear levels than some of the other oils in the database. In most cases, the difference is not statistically significant, although there was one case where Pennzoil Platinum showed significantly better iron wear levels than Mobil 1.
- There is adequate data to support the high regard BITOG members have for Pennzoil Platinum oil. In those cases where a direct comparison could be made, Pennzoil Platinum showed reduced iron levels compared to other oils, although these differences were not always statistically significant.
- American designed and manufactured 6 cylinder and 8 cylinder engines tended to show higher iron levels than Japanese and German engines.
By OldCowboy
The first 60 pages of 20 weight and 30 weight UOAs have been compiled into a spreadsheet database. This is too much data to present in a forum topic, but the data will be provided to anyone who sends me a PM.
The following criteria were used to determine if a UOA was excluded:
- Samples with unit mileage less than 20,000 were not included based on the assumption that they may still be showing high wear levels due to ongoing break-in.
- Samples with additives (MMO, Auto-RX, etc.) were not included due to unknown effects of the additive.
- Samples with make-up oil were not included. This is because I had no way of knowing what effect the addition of make-up oil had with regard to the wear metals.
- There is only one sample included per OP/engine/oil combination to ensure the data were not skewed by multiple nearly-identical samples.
- Samples that did not have iron as the highest wear metal were not considered unless the UOA indicated that this was a normal condition for that particular type engine.
- Samples that had significant fuel or water contamination were not considered due to higher than normal wear to be expected from these samples.
- Samples with less than 2000 miles on the sample were not included.
- Samples which did not have the engine identified and could not be determined via Internet search were not included. This occurred when a model had multiple engines available.
At this time there are 245 samples in this database.
- 112 samples from 4 cylinder engines (34 w/ 20 wt and 78 w/ 30 wt)
- 87 samples from 6 cylinder engines (22 w/ 20 wt and 65 w/ 30 wt)
- 46 samples from 8 cylinder engines (17 w/ 20 wt and 29 w/30 wt)
The database contains the following data fields:
Motor Oil & Viscosity
Wear Metals (Fe, Cr, Ni, Al, Cu, Pb, Sn), normalized to ppm/1000 miles
Original Poster of the UOA
Date the UOA was posted
Engine Make and Displacement
Oil Mileage
Unit Mileage
It has been stated in many documents/references that iron is the only wear metal which consistently increases as mileage increases. Therefore, this white paper will only focus on iron wear levels.
4 CYLINDER ENGINES
20 Weight vs. 30 Weight - Iron ppm per 1000 miles
Code:
20 Weight 30 Weight
Minimum Value 0.50 0.44
Maximum Value 3.24 4.76
Average Value 1.48 1.61
Standard Deviation 0.71 0.96
95% Confidence Value 0.50 0.21
95% Confidence Interval 0.98-1.98 1.40-1.81
Number of Samples 34 78
The 30 weight oils had a larger spread in iron wear levels (0.44 - 4.76 vs. 0.50 - 3.28) and a slightly higher average value (1.61 vs 1.48). However the 95% confidence value for the 30 weight oils was smaller (0.21 vs 0.50), mainly due to the larger sample size. It should be noted that the mix of engines in both the 20 weight and 30 weight UOAs was very similar.
The 95% Confidence Intervals for the 20 weight samples and 30 weight samples overlap. Thus, there is probably no statistically significant differences in the iron wear levels between 20 weight and 30 weight oils in the 4 cylinder engines reported in these UOAs. A student'sT-test run on this data indicated that the iron wear levels between the 20 weight and 30 weight oils were NOT statistically different at the alpha = 0.05 level.
Differences Among 20 Weight Oils
There were some noticeable differences in iron wear levels between the various 20 weight oils reported in these UOAs. However, many of the oils were only represented by two or three sample reports. It was arbitrarily decided to only perform statistical comparisons on oils that had five or more sample reports.
Among the 20 weight oils, only two oils had five or more samples reported. These were Amsoil and Mobil 1. The statistical data associated with these two oils are shown here:
Code:
Amsoil 20 Mobil 1 20
Minimum Value 0.50 1.02
Maximum Value 1.80 3.10
Average Value 1.10 1.81
Standard Deviation 0.52 0.70
95% Confidence Value 0.42 0.49
95% Confidence Interval 0.68-1.52 1.32-2.30
Number of Samples 6 8
There is only a slight overlap of the 95% Confidence Interval between these two oils, so a student's T-test comparing the two sample groups was conducted. According to the T-test, there was a statistically significant difference between the two sample groups with an alpha value of 0.05. Thus, it can be said that the Mobil 1 20 weight sample group shows more iron than the Amsoil 20 weight sample group with a confidence of 95%.
Differences Among 30 Weight Oils
Five oils in the 30 weight oil group had five or more UOAs reported. The summarized data is presented below:
Code:
Amsoil Castrol Edge Castrol Syntec
Minimum Value 0.59 0.73 0.67
Maximum Value 4.37 2.95 2.77
Average Value 1.80 1.56 1.72
Standard Deviation 1.15 0.88 0.80
95% Confidence Value 0.75 0.71 0.64
95% Confidence Interval 1.04-2.55 0.85-2.26 1.08-2.36
Number of Samples 9 6 6
Mobil 1 Pennzoil Platinum
Minimum Value 1.15 0.44
Maximum Value 4.39 3.67
Average Value 2.32 1.28
Standard Deviation 1.08 0.91
95% Confidence Value 0.64 0.56
95% Confidence Interval 1.68-2.96 0.71-1.84
Number of Samples 11 10
There is significant overlap in the 95% Confidence Intervals of all of these sample groups. However, there is the least overlap between Mobil 1 and Pennzoil Platinum. A student's T-test shows that the Mobil 1 sample group shows higher iron wear levels than the Pennzoil Platinum sample group at an alpha of 0.03. This is a statistical significance at the 97% level. None of the other sample groups showed a significant difference as compared to Pennzoil Platinum. Additionally, none of the other sample groups showed a significant difference as compared to Mobil 1.
The 30 weight sample groups can be ranked in the following order, from lowest to highest iron wear levels:
Pennzoil Platinum < Castrol Edge < Castrol Syntec < Amsoil
Comparison of Amsoil and Mobil 1 20 weight vs 30 weight
Since both Amsoil and Mobil 1 had appropriately large sample groups in both 20 weight and 30 weight viscosities, the obvious question is which viscosity produces the least iron wear. This comparison is shown below:
Code:
Amsoil 20 Amsoil 30
Minimum Value 0.50 0.59
Maximum Value 1.80 4.37
Average Value 1.10 1.80
Standard Deviation 0.52 1.15
95% Confidence Value 0.42 0.75
95% Confidence Interval 0.68-1.52 1.04-2.55
Number of Samples 6 9
Mobil 1 20 Mobil 1 30
Minimum Value 1.02 1.15
Maximum Value 3.10 4.39
Average Value 1.81 2.32
Standard Deviation 0.70 1.08
95% Confidence Value 0.49 0.64
95% Confidence Interval 1.32-2.30 1.68-2.96
Number of Samples 8 11
Both oils show lower average wear levels in the 20 weight sample group than the 30 weight sample group. A student's T-test shows that neither of these 20 weight oils is statistically different than their 30 weight counterpart at an alpha = 0.05 level.
6 CYLINDER ENGINES
20 Weight vs. 30 Weight - Iron ppm per 1000 miles
Code:
20 Weight 30 Weight
Minimum Value 0.60 0.61
Maximum Value 6.57 19.02
Average Value 1.82 2.72
Standard Deviation 1.20 3.00
95% Confidence Value 0.76 0.66
95% Confidence Interval 1.06-2.59 2.06-3.38
Number of Samples 22 78
The 20 weight sample group had significantly lower iron levels as measured by a student's T-test at an alpha = 0.05 level. The mix of engines in the 30 weight sample group differed from the 20 weight group in that the 30 weight group had engines from GM and Chrysler that were not present in the 20 weight group. These engines tended to have higher iron levels than the Ford, Honda, Mitsubishi, Hyundai, Kia, Toyota, and GM 3.6L engines in the 20 weight group. Therefore, I stripped all Chrysler and non-3.6L GM engines out of the 6-cylinder 30 weight sample group and reexamined the 20 vs 30 weight question with these results:
Code:
20 Weight 30 Weight
Minimum Value 0.60 0.62
Maximum Value 6.57 11.83
Average Value 1.82 2.15
Standard Deviation 1.20 1.95
95% Confidence Value 0.50 0.56
95% Confidence Interval 1.32-2.32 1.58-2.71
Number of Samples 22 46
When the Chrysler and non-3.6L GM engines are removed from the 30 weight samples, there is no significant difference between the 20 weight and 30 weight oils. This adjusted 30 weight sample group will be used for the remaining 6 cylinder statistical comparisons. It should be noted that both the range of values and the average value dropped when Chrysler and non-3.6L GM 6 cylinder engines were removed from the sample group.
Differences Among 30 Weight Oils
Only three 30 weight oils had the requisite number of samples for statistical comparison; Mobil 1, Pennzoil Platinum, and Pennzoil Ultra:
Code:
Mobil 1 Penn Plat Penn Ultra
Minimum Value 0.62 0.89 0.79
Maximum Value 8.00 3.69 3.66
Average Value 3.01 1.44 1.59
Standard Deviation 2.80 0.93 1.18
95% Confidence Value 2.24 0.64 1.03
95% Confidence Interval 0.77-5.25 0.80-2.08 0.56-2.62
Number of Samples 6 8 5
Given the major overlap in the 95% Confidence Intervals of the three sample groups, it comes as no surprise that student's T-tests comparing the three sample groups shows no significant differences.
Comparison of Pennzoil Platinum 20 weight vs 30 weight
Pennzoil Platinum is the only oil with enough samples in both viscosities to allow a statistical comparison:
Code:
Penn Plat 20 Penn Plat 30
Minimum Value 1.12 0.89
Maximum Value 2.20 3.69
Average Value 1.53 1.44
Standard Deviation 0.39 0.93
95% Confidence Value 0.31 0.64
95% Confidence Interval 1.22-1.84 0.80-2.08
Number of Samples 6 8
Because the 95% Confidence Interval for the 20 weight Pennzoil Platinum samples is totally contained within the 95% Confidence Interval for the 30 weight Pennzoil Platinum samples, there is no significant difference between the iron wear levels of these two oils.
8 CYLINDER ENGINES
20 Weight vs. 30 Weight - Iron ppm per 1000 miles
Code:
20 Weight 30 Weight
Minimum Value 0.63 0.65
Maximum Value 7.00 7.60
Average Value 2.45 2.73
Standard Deviation 1.66 1.98
95% Confidence Value 0.79 0.72
95% Confidence Interval 1.66-3.24 2.01-3.45
Number of Samples 17 29
The 8 cylinder 20 weight sample group consisted of engines from Ford and Chrysler. The 8 cylinder 30 weight sample group consisted of engines from Ford, Chrysler, Toyota, GM, and Nissan.
Both the overlap of the 95% Confidence Intervals and a student's T-test show that there is no significant difference between the 20 weight samples and the 30 weight samples.
Comparison of Amsoil and Mobil 1 30 weight
The only oils which had enough samples to compare were the Amsoil 30 weight and the Mobil 1 EP 30 weight:
Code:
Amsoil 30 Mobil 1 EP 30
Minimum Value 0.65 0.76
Maximum Value 5.00 6.73
Average Value 2.35 3.31
Standard Deviation 1.52 2.94
95% Confidence Value 1.21 2.57
95% Confidence Interval 1.14-3.56 0.74-5.88
Number of Samples 6 5
Both the overlap of the 95% Confidence Intervals and a student's T-test show that there is no significant difference between the Amsoil 30 weight samples and the Mobil 1 EP 30 weight samples.
Comparison of 20 weight vs 30 weight oils - Ford and Chrysler V8 Engines
Because the 30 weight group had a different mix of engines than the 20 weight group, the Toyota, GM, and Nissan engines were removed from the 30 weight group and the comparison was repeated:
Code:
20 Weight 30 Weight
Minimum Value 0.63 2.00
Maximum Value 7.00 7.60
Average Value 2.45 4.25
Standard Deviation 1.66 2.09
95% Confidence Value 0.79 1.37
95% Confidence Interval 1.66-3.24 2.88-5.61
Number of Samples 17 9
When Ford and Chrysler V8 engines are compared using 20 weight vs 30 weight oils, the 20 weight sample group showed lower iron levels at the alpha = 0.04 level. This is a 96% significance level. It should be noted that the average iron wear value increased when the Japanese and German V8 engines were removed from the sample group.
GENERAL OBSERVATIONS
- 20 weight oils consistently showed lower average iron levels than 30 weight oils. The only time this difference was statistically significant was with Ford and Chrysler V8 engines.
- Mobil 1 oils tend to show higher iron wear levels than some of the other oils in the database. In most cases, the difference is not statistically significant, although there was one case where Pennzoil Platinum showed significantly better iron wear levels than Mobil 1.
- There is adequate data to support the high regard BITOG members have for Pennzoil Platinum oil. In those cases where a direct comparison could be made, Pennzoil Platinum showed reduced iron levels compared to other oils, although these differences were not always statistically significant.
- American designed and manufactured 6 cylinder and 8 cylinder engines tended to show higher iron levels than Japanese and German engines.