5w30 Instead Of 10w30 Oil Weight ?

Discussion in '1994 - 1995 Specific Tech' started by Killa, Aug 15, 2012.

  1. My 5.0 factory call for 10w30, can I use 5w30 ?
  2. why would you want to?

    wait check that. i read it wrong. are you sure it says 10w30? think it should be 5w....
  3. the owner manual came with the 95 gt say 10w30, and 5w30 if under 0* , so i guest 5w30 is good for all year round then, reason i want use 5w30 because my 3 my family car using same oil and same weight, and I want the mustang using same weight too.
  4. use what it says, unless you have changed something that needs a different weight oil. although the 5w or 10w does not matter except for cold start applications.
  5. Newer engines have closer tolerances and benefit from the thinner oil. Older push rod engines do better with the thicker 10-30. The folks at Ford who came up with the requirements are engineers! If it ain't broke don't fix it.
  6. Changes between the old engine and new aren't really that different to be honest. I remember when building my last 4.6L, all of the tolerances were pretty much in line with the old 5.oL OHV it replaced.

    Ford went to thinner oils with the OHC to promote quieter cold starts (hydraulic actuators make the timing chains rattle like crazy until oil pressure comes up) and to promote fuel economy (thinner oil creates less drag and consumes less horsepower) than anything else. The difference offered between the different grades as far as protection goes is insignificant at best.
  7. I've always used 5w30 in all my Mustangs, you'll be fine. However, I live in southern California so it doesn't get cold enough to really make a difference in the two oils.
  8. The only difference between 5w30 and 10w30 of the same brand will be the viscosity when cold. The "W" designation stands for "Winter." At operating temp there will be no difference.
  9. Ok, just to clarify, the second number is the "winter" viscosity. 5W-30 has twice the viscosity of 10W-30 at operating temperatures.

    fess40 likes this.
  10. No the first number is Winter. You want thin oil when cold to get it up to the valve train, then thicken up at operating temperatures.
  11. Whoever gave you that information is sorely mistaken. 5W30 and 10W30 in a same brand will have the same viscosity at operating temperatures, but the 5W30 will have less resistance to flow when cold as opposed to 10W30.

    Now certain brands of oil will have different thicknesses within a viscosity grade. German Castrol, aka Castrol Syntec 0W30 is almost a 40 weight at operating temps.
  12. So you are saying oil will drip through a viscosimeter faster when it is cold that when it is hot???

  13. No what I am saying is that the multi viscosity ratings of modern oil lists the viscosity of 0 degrees C as the first number. Think about it, Ford uses 5W20 in the majority of their newer engines, they do it because it is thinner at operating temps and therefore they get a higher CAFE rating. They use 5W30 in the Ecoboost motors because of the turbochargers and the oil is thicker at operating temps. Same reason why the new GT500's and BOSS 302's take Motorcraft 5W50 for the increased protection at operating temp.

    If you don't believe me that is fine, but you should educate yourself on oil analysis and understand how the SAE oil viscosity ratings work. Also if you don;t believe me, rest assured because EVERY oil manufacturer agrees with me, because that is the information they use.

    Back on topic, either weight is fine really. The literal only differenceis the viscosity when cold between a 5W30 and 10W30. On a pushrod motor that is not as critical as a OHC motor.
  14. Oil weight is based on the Saybolt viscosity test. With a Saybolt viscosity test, the oil is at a given temperature, and is placed in a container with a fixed orifice at the bottom. Something that looks like this.


    The time it takes for a given volume of oil to run through the viscosimeter is measured in seconds, now referred to as Saybolt seconds. This time is then divided by 10 for Aviation grade oil, and by 20 for Automotive grade oil. So if it takes 1000 Saybolt seconds for the oil to go through, then it is 100 Weight Aviation oil, and 50 Weight Automotive oil. The oil is then heated up to a given temperature, and run through again for the hot test. Obviously hot oil is going to pass through an orifice faster than cold oil. Just compare how fast the oil drains out of your car when you pull the oil drain plug when it is warm compared to when it is cold. So the first number is the hot number, obviously being thinner oil. For the purpose of this discussion the first number is the most relevant, because when the car is hot and running on 5W-30 vs 10W-30, the oil will be twice as thin.

  15. I read that Amsoil thing, they have got that all messed up.

  16. This ^. There are two temperature range characteristics that are tracked for multi-weight motor oil. Cold characteristics and operating temperature characteristics. 5w flows more easily than 10w at the same cold temperature. Both flow equally at the same operating temperature.

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  17. I think it's an over complicated description in which they have copied data from the same source. Your trying to argue something that defies common knowledge. By your logic, 20W-50 is thinner than 10W-30.