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Thread: Very cold weather. 5w30 dino or 10w30 synthetic

  1. #1
    Helpfull BT forum member Swabie
    Join Date
    Sep 2008

    Very cold weather. 5w30 dino or 10w30 synthetic

    The weather here has been very cold. High for the day 7 F. 10w30 Rotella oil is a little to thick for starting. I'm debating on using either 5w30 dino or 10w30 Mobil 1. Both with comp cams additive for the cam. My 401 has about 2500 miles on it. Any recommendations?

  2. #2
    Thank you from BT Tech Master Bulltear Forum
    Join Date
    Jan 2003
    s.e. minnesota
    I use 10W30 dino in my 360 all winter, but it's a worn motor with 107K on it.
    parting several FSJ'S

  3. #3
    Thank you from BT Tech Master Bulltear Forum
    Join Date
    Nov 2005
    Middle of the Iron Range MN
    I just stick with my 15-40 until it gets really cold which for me is well below 0F. Then I switch to 10-30/40. I have never had a problem getting my jeep started even at temps around -40 regardless of which oil I have in it. I have found that the most important thing for winter starting is to have a good battery and a good starter. I get the biggest battery that I can with the most cold cranking amps, in my case I have two interstate Megatrons for total of over 1600CCA's and I have the ability to self jump-start with my setup.

    Till the temp gets below zero I dont worry about things getting too stiff but if you are I would use think about the dyno oil. It doesnt seem to stick to the cylinders as much and in my experience with my truck might crank a little easier. Never had a problem with the truck(chevy 2500) starting in the winter till I started using synthetic. It sticks to the cylinders more and seems to crank harder on really cold nights than it ever used to on dino. semi-synth seems to be a good compromise.

  4. #4
    Thank you from BT ULTIMUS MAXIMUS STATUS tufcj's Avatar
    Join Date
    Apr 2004
    Watkins, CO
    I run 10W40 year around in my CJ. It's never failed to start.

    A lot of people don't understand oil ratings on the multi visc oils. The W in 10W40 stands for winter. The low number is the cold rating, any 10W oil being no thicker than a straight 10 weight oil when cold. The high number is the hot rating, meaning a 10W40 would be no thinner than a straight 40 weight oil when hot. A 10W30 would be thinner than 10W40 when hot. Both a 10W30 and 10W40 should technically flow the same when cold.

    I personally don't know if I'd use a 5W oil, synthetic or dino, in an older motor. Clearances and tolerances are designed looser than the modern engines that suggest the 5W30 oils.

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  5. #5
    Thank you from BT Tech Master Bulltear Forum
    Join Date
    Sep 2003
    Is the 10W30 recommended for the 360 (dino oil). Would you want the 10W30 as opposed to the 10W40, thinner to get in between the surfaces etc. All year round? As I read more and more about the AMC oiling/problems that seem to me occur easily I'm inclined to go w/the 10W30 dino.

    What say ye!
    84' CJ8-360-Project M170 Jeep
    86' CJ7-258-Mommas Jeep
    Project CJ8 to M170 Conversion<----Click

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