Just a quick question, does the oil weight by gallon either higher or lower make any difference in the quality of the oil? I noticed Castrol Syntec 5w20 and 5w30 were much different. The 5w20 is much heavier (almost seems like a typo). 7.8 vs. 7.2 lbs/gal. What would you choose? I can use either one.
Does oil weight (lbs) by gallon make a difference?
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Originally Posted By: chubbs1
Just a quick question, does the oil weight by gallon either higher or lower make any difference in the quality of the oil? I noticed Castrol Syntec 5w20 and 5w30 were much different. The 5w20 is much heavier (almost seems like a typo). 7.8 vs. 7.2 lbs/gal. What would you choose? I can use either one.
No difference, oil does lighten with heat.
It may very well be a typo, other than that could be packaging or physics at work.
Somebody else knows more about this.
Just a quick question, does the oil weight by gallon either higher or lower make any difference in the quality of the oil? I noticed Castrol Syntec 5w20 and 5w30 were much different. The 5w20 is much heavier (almost seems like a typo). 7.8 vs. 7.2 lbs/gal. What would you choose? I can use either one.
No difference, oil does lighten with heat.
It may very well be a typo, other than that could be packaging or physics at work.
Somebody else knows more about this.
I would not be overly concerned about density when choosing oil.
Density is considered as a "low-importance" characteristic of engine oil. It can be helpful in determining the rate of change kinematic viscosity as the temperature increases; but who really wants to calculate that?
This is why it is rare to find density listed on PDS for oils intended for gasoline engines
It does play more of an important role in some industrial oils; but for new engine oils it is about as important as the color or odor. There could be many reasons why your 5w20 is more dense (to avoid confusion with heavier) than 5w30 - blend of base stocks, percentage of additives etc etc. Don't worry about it, focus on the performance aspects instead.
This is why it is rare to find density listed on PDS for oils intended for gasoline engines
It does play more of an important role in some industrial oils; but for new engine oils it is about as important as the color or odor. There could be many reasons why your 5w20 is more dense (to avoid confusion with heavier) than 5w30 - blend of base stocks, percentage of additives etc etc. Don't worry about it, focus on the performance aspects instead.
I did not keep some articles I saw once showing that a more dense oil has more forces separating parts. I have noticed that the oils I like most have higher densities than other oils even within the same grade. I now look at this oil specification as one worth noting in the decision process regarding what oil to try next.
aehaas
aehaas
The density of base oils varies widely. Here are some typicals for base oil grades used in motor oils, in lbs/gal:
PAO........6.8 - 6.9
Grp III.....6.9 - 7.0
Grp II......7.1 - 7.2
Grp I.......7.2 - 7.3
AN..........7.5 - 7.6
Esters......7.6 - 8.3
As you can see, the density varies with chemical structure and there is no simple correlation of density with base oil performance.
The additive package also contributes significantly to the finished oil density as metallic detergents can be quite dense.
Tom NJ
PAO........6.8 - 6.9
Grp III.....6.9 - 7.0
Grp II......7.1 - 7.2
Grp I.......7.2 - 7.3
AN..........7.5 - 7.6
Esters......7.6 - 8.3
As you can see, the density varies with chemical structure and there is no simple correlation of density with base oil performance.
The additive package also contributes significantly to the finished oil density as metallic detergents can be quite dense.
Tom NJ
Tom thanks for that.
I think the reason some equate high density oils as providing some additional protection in some way is because oils with a known high ester content also happen to have, not surprisingly, higher densities. It is also a characteristic of ester based oils to have higher HTHSVs relative to their KV100 spec's but it would seem to make more sense to simply compare the actual HTHSVs of different oils, regardless of their base oil chemisties and net densities, to determine which oils have the higher film strengths.
I think the reason some equate high density oils as providing some additional protection in some way is because oils with a known high ester content also happen to have, not surprisingly, higher densities. It is also a characteristic of ester based oils to have higher HTHSVs relative to their KV100 spec's but it would seem to make more sense to simply compare the actual HTHSVs of different oils, regardless of their base oil chemisties and net densities, to determine which oils have the higher film strengths.
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