confused about my favorite synthetic oil

Discussion in 'Mechanic and Repair' started by Envy Lawn Service, Jan 18, 2003.

  1. Envy Lawn Service

    Envy Lawn Service LawnSite Fanatic
    Posts: 11,062

    I have to admit I've became a "fleet" oil lover. I was running Chevron Delo 400 15W-40 oil in everything. Quite a while back I converted everything of mine but one car over to Shell Rotella T synthetic 5W-40.

    Recently I switched the car over as well. I don't like the results at all. For some reason the car knocks during cool morning starts (below freezing). Everything else has been doing fine with the synthetic. What gives????

    I consider myself well educated about oil. But this one has me puzzled. I only have a few "maybe" answers floating around in my head....
     
  2. Bunton Guy

    Bunton Guy LawnSite Bronze Member
    Posts: 1,762

    The synthetic oil your using is going to start out in the morning to be a little thicker just think of molasis...basically like that. That is why your engine is knocking as much as it is. I would switch back to a non synthetic during winter months and back to a synthetic during spring/summer when its needed for the high temps.
     
  3. Envy Lawn Service

    Envy Lawn Service LawnSite Fanatic
    Posts: 11,062

    I chaged from 15W-40 to 5W-40 synthetic. Why would the 5W-40 be thicker?

    I'm thinking more along the lines that it's so thin that it all drains down overnight, leaving less oil up in the engine in the morning. So it's not there 1st thing when I crank up. The car is different from the other engines I run it in because it's a DOHC as well. Also I don't believe the filter for it has an anti-drainback valve like are on the other stuff.

    :confused:
     
  4. 65hoss

    65hoss LawnSite Fanatic
    Posts: 6,360

    You need a 30 weight this time of year. Not the 40. That is why its so thick.
     
  5. Alan Bechard

    Alan Bechard LawnSite Member
    Posts: 175

    The W in this scenario stands for Winter. Which is the rough equivilant to the SAE weight of the oil during the winter months.

    Al B
     
  6. Bunton Guy

    Bunton Guy LawnSite Bronze Member
    Posts: 1,762

    Envy when I said thicker I meant synthetics are generally thicker in cold weather.
     
  7. Envy Lawn Service

    Envy Lawn Service LawnSite Fanatic
    Posts: 11,062

    It was to my understanding that the "W" stood for the weight of the base stock of the oil....

    5W-40
    A 5 weight base stock with an additive package that will not allow it to thin more than a 40 weight would thin to at "x" degrees.

    15W-40
    A 15 weight base stock with an additive package tha will not allow it to thin more than a 40 weight would thin to at "x" degrees.

    The 15W-40 that came out of the car is much much thicker than the 5W-40 I put in it. I had no chatter at much colder temps with the 15W-40. It chattered at 35 degrees today!
     
  8. mmathys

    mmathys LawnSite Member
    Posts: 13

    A 5W40 has the same viscosity at 100C as a straight 40, a 10W40, and 15W40, etc.

    At low temps it has the same viscosity as an SAE 5. W from winter means it performs well at low temperaturs.

    5W40 oils usually have a pour point around -50F or lower. There is no way that synthetic oils are thicker at cold temps, the fact that then do not thicken on of their biggest advantages.

    If you have a noise is supect that you could have gotten the wrong filter. If you filter mounts upside down they usually have a bleed-back valve that keeps the oil from draining out when the engine is shut off. Otherwise it has to fill the filter first so you may hear some lifter noise (tapping). If it is a true knock, they usually come from connecting rod bearings and indicate a more serious problem.

    Good Luck

    Mark
     
  9. ksland

    ksland LawnSite Senior Member
    Posts: 927

    Your Butt backwards there mm
     
  10. mmathys

    mmathys LawnSite Member
    Posts: 13

    Please explain where I am wrong?

    Mark
     

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