API motor oil standards?

Discussion in 'Small Block Tech' started by Blurredman, Nov 21, 2018.

  1. Blurredman

    Blurredman Well-Known Member

    I am using 20w50 which is an API of SE in my '80 350 LeSabre.

    I don't particular want to be using that high a weight of oil in the winter really. And rather the 10/40 recommended in my owner's manual. However, SE classifications of oil are only available in 20w50 form these days where I am from (UK) without paying stupid prices for import stuff.

    I mainly use this oil for the proposed zinc content that is apparently required. And would gladly change for the above reasons.

    I have found a 30 weight that I can get bulk in cheap, but is API of SD! And of course- zinc is not listed, of course.

    In forum member's opinions, do they stick with API standards, or perhaps use makes of oil with guarenteed ZDDP/Zinc content regardless of API standards? As far as I'm aware, The newer 'editions' of oil standards normally contain less of the material an older motor might need.

    According to what I can find, the classification after G is where zinc was reduced. So.. I could use a normal 10w40 F or G?

    Last edited: Nov 21, 2018
  2. partsrparts

    partsrparts Silver Level contributor

    Valvoline Racing oil has a high zinc content. The 10/30w is real common at pretty much all auto part stores in the US. There are also bottles of zinc additive you could add to other oils. I just don't know how available it is in the UK.
  3. Luxus

    Luxus Gold Level Contributor

    I personally use the correct weight per the owners manual but use a zinc additive. There are also small oil companies that do make oil with high zinc in it. You won't find them in stores, but if you search online you will find them.
  4. Blurredman

    Blurredman Well-Known Member

    Okay, I'm starting to understand it now, although I am finding contradicting entries on the internet as to how much zinc one might need.

    So, the consensus is that you can use modern oils, so long as you use an additive. How much zinc content (plus additive) would be permissable to use?

    For example, I found this oil here:

    modern oil at SL classification, but has a zddp of 1,300ppm...

    But then I find oil with over 2,000. How much zinc should this age of engine require, and- what about too much? Is there an upper limit?

    Thank you for your responses.
  5. Houmark

    Houmark Well-Known Member

    Hey.. I've used oil from 5w30 to 15w40, always togtheter with a bottle of zddp, without ever having problems.. These old engines don't require alot in stock form..

    My advice is to use what you want, and put a bottle zddp in, that way you're sure you have above 1200ppm, which apperently is the magic number as far as I recall..
  6. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

  7. gstewart

    gstewart Well-Known Member

    20W50 - that is for old Jaguars or u live in a desert. I use Castrol GTX 10W40 & ZDDP additive..
  8. gsjohnny1

    gsjohnny1 Well-Known Member

  9. 1973gs

    1973gs Well-Known Member

    If you have to use a zinc additive, you're using the wrong oil. Any sn/sm oil not only doesn't contain any zinc, it will remove the zinc from your block. You can buy Valvoline vr 10 w 30 (and other brands and weights ) on Amazon cheap. Use the correct oil.
  10. jay3000

    jay3000 Well-Known Member

  11. Schurkey

    Schurkey Silver Level contributor

    A stock engine doesn't have enough valve spring to need hot-rod oil.

    20W-50 is WAY TOO THICK.
  12. OddfireV6

    OddfireV6 Active Member

    It's amazing that you can buy API SD and SE oil in the UK. About the oldest API classification that can be found here in the US is SJ or SL.

    I run Quaker State 10W30 high mileage oil in my engines. It used to be called "defy" and was specifically developed by QS for use in flat tappet engines. QS has since removed the "defy" name and reduced the ZDDP levels, but the levels are still higher than most regular SN oils. It is 900 PPM Zinc and 650 PPM Phosphorus. My Buick ran on nothing but this oil until I tore the engine apart after 6000 miles. The cam and lifters showed zero wear, so I reinstalled them. And no, there was no sludge formation as the haters of Pennsylvania grade crude often claim. Pennzoil and Quaker State probably are not even using Penn grade crude any more.

    I've been switching over to Rotella T4 10W30 lately because my place of employment sells it and I get an awesome price as an employee. It's higher ZDDP than the Quaker State.

    Buicks with stock valve springs and cam profiles do not load their lobe and lifter surfaces enough to need levels of ZDDP above the API SN standard, but I like having a little more ZDDP anyway as an insurance policy.

    Buicks tend to have lower oil pressure than most owners are used to, so the owners combat this by using a thicker oil like 20W50 to increase oil pressure. That is not the best idea in the world, because a properly built Buick has very tight bearing clearances that require a thinner oil to achieve proper bearing lubrication. Bearings are cooled by the oil flowing through them. Tight bearings flow less oil and thicker oil flows less. Less oil flowing through the bearing means the bearing runs hotter and that also heats the oil. It's not a good situation.
    Blurredman likes this.

Share This Page