Any Reason Not To Use A 5W-30 Instead of a 10W-30?

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Rhoyd

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I drive a '93 Ford 5.8L (351 cid) with a 6 lbs. supercharger and a '99 Nissan 3.0L V6.

Both vehicles are lubricated with conventional motor oil.

Both are driven in the Tampa, FL area.

Both vehicles typically get exceedingly frequent oil changes and never, ever over 3K.

Both owner's manuals call for either the 5W or the 10W depending on ambient temps.

I can't see any reason not to use a 5W all the time and would like the extra flowability at stratup.

Can anyone give me a reason or two why this is not a good idea?
 
I completely agree. If we are talking about the same oil manufacturer, oil group, and product class, then I would argue that a 5w-30 is always better than a 10w-30.
 
With today’s motor oils, the “flowability” of a 10W-30 vs. a 5W-30 is a lot closer than most folks realize.
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10W-30’s tend to lag or be thicker than 5W-30’s by about a 10F degree differential.

Code:


Viscosity in cSt

TEMP Havoline Havoline

C F 5W-30 10W-30

0 32 573 814

5 41 403 556

10 50 293 389

15 59 218 280

20 68 165 206

25 77 127 155

30 86 100 118






So looking at 59F degrees, if the oil pump has flow problems with the 280 cSt of a 10W-30, it will have the same problems with a 5W-30 at 50F degrees.

- Just my
twocents.gif
, but I think the performance of 10W-30 & 5W-30 are very similar, with 5W having an advantage in cold weather & 10W in hot temperatures & high engine temp situations like towing.
 
If you vehicles had twins and you ran one group on 10w and the other on 5w it might be hard to tell the difference. If thinner is better, and it usually is, the 5w-30 is the choice, by what ever small margin that may be. With such frequent oil changes you might want to pick something else to worry about. I think you have the oil covered. How about moving the interval to 5k miles?
 
Quote:

Both owner's manuals call for either the 5W or the 10W depending on ambient temps.

I can't see any reason not to use a 5W all the time and would like the extra flowability at stratup.

Can anyone give me a reason or two why this is not a good idea?

Click to expand...


Look at the specs of the 5w30 and the 10w30 you'd like to use. Unless the 10w30 has a higher flashpoint and HTHS, and a lower NOACK, the 10w30 doesn't provide any advantage in warmer weather or for towing. And if the 10w30 is made with lower quality basestocks, it may actually be at a disadvantage since it may leave slightly more deposits.
 
The current Pennzoil data sheet gives an indication of the slight high temp performance advantage that a 10W-30 gains by having a small percentage of heavier base oil than the 5W-30's.


Code:


Pennzoil 5W-30 10W-30



Flash Point 216C 221C



Noack

Volatility % 14.7 10.9






However, the differential in Noack spreads is generally more like 2-3 points, and many companies do not list the actual value, but rather indicate “less than” the 15% GF-4/SM requirement.
 
Down in Tampa the 10W-30 may have a slight thermal stability performance advantage. Not a lot but you will never need the advantages of the 5W except for maybe the 1 or 2 days every other year or so.
 
You are running 6# of boost pressure into an old school V8 and want to run 5W30 on the street in FL. DId I get the facts correct? I think you are not wise to run a dino 5W30 in your bosted application. The forced induction is going to creat a need for an oil with higher HTHS numbers then what is typicaly seen in 5W30 dino oil! If not for your forced induction in the examples you gave I would not have a problem with anyone running 5W30 in place of 10W30. Cold flow and pumbabilty are laughable concerns below the mason dixie line.
 
Quote:


The current Pennzoil data sheet gives an indication of the slight high temp performance advantage that a 10W-30 gains by having a small percentage of heavier base oil than the 5W-30's.


Code:


Pennzoil 5W-30 10W-30



Flash Point 216C 221C



Noack

Volatility % 14.7 10.9






However, the differential in Noack spreads is generally more like 2-3 points, and many companies do not list the actual value, but rather indicate “less than” the 15% GF-4/SM requirement.

Click to expand...


Interesting you would find the one brand where there's a very slight advantage in the published specs, but it's only for the NOACK. The FP and HTHS differences are insignificant. If one looks at others brands like MC, TropArtic, Valvoline, Mobil 5000/7500, Havoline, we find no significant advantage.

Further, with the 5w30 grade, one can also look for the Ford WSS-M2C929-A spec which specifies additional requirements above GF-4 on the 5w30 grade that is not required of the Ford's WSS-M2C205A spec for the 10w30 grade.
 
Quote:

Cold flow and pumbabilty are laughable concerns below the mason dixie line.

Click to expand...


Just as laugable as someone thinking that 10w30 dino is going to provide any significant HTHS advantage over 5w30 dino.
laugh.gif
 
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