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5W30 vs 10W30

I took my 1995 Mustang GT in today for an oil change. The owner's manual specs 10W30 for temps above 0. The shop put in 5W30, spec'd for temps below 0 and listed as "acceptable" up to 60 F. It was in the 70's today. Should I make him change it out?

Comments

  • edited November 2008
    I am not an expert like some guys here, but most cars can run fine on 5W30. The first number tells you how it works when it is REALLY cold. The second number tells you how it works when it is hot. Note hot is the same viscosity rating.

    Read carefully the opinion of others. Usually one tries to follow the manual. I am just not sure it matters that much.
  • edited November 2008
  • edited November 2008
    You would not want to take a very long very fast drive in very hot temps, but frankly there is little difference. Both oils should react about the same at operating temperature.

    The 5 vs 10 part of the designation is how the oil acts when cold, it is not material to how the oil acts at operating temperature. The 5W30 oil will start a little easier and will get the oil to the engine a little faster on cold starts.

    Both oils will react the same at operating temperature.

    The 10W30 will break down a little faster due to additional additives (less oil) but modern oils, especially synthetics, are so good that there is no real difference at all.
  • edited November 2008
    The "30" part of 5W30 and 10W30 is the high temperature range, and they are the same. The "5" part means the oil will flow more easily at low temperatures, which is a good thing. You have nothing to worry about.
  • edited November 2008
    The two numbers represent the "pour point" flow characteristics for oil temperatures of 0 and 100 degrees centigrade.

    The "5" in the 5W30 means the oil will have the same "pour point" flow characteristics as a straight 5 weight oil at 0 degrees C.

    The "30" in the 5W30 means the oil will have the same "pour point" flow characteristics as a straight 30 weight oil at 100 degrees C.

  • edited November 2008
    Joe, you didn't really mean that last statement did you? Its the 5w30 that breaks down a little faster because it has less oil and more VIs.
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