SL vs. SM in older engines w/flat tappet cams

[conradcliff]

Hey guys, so I was doing some reading and I found this article someone sent it to me or something, but about half way down the page it starts talking about SM rated oils being bad for engines with flat tappet cams b/c the SM rated oils dropped the level of ZDDP which is used for protecting the cam under it's extreme pressures.

What do you guys think? If we do need to keep using SL rated oils, which ones are still using this rating and are they on their way out? And if they are on their way out, what additive would be best to use to increase the ZDDP?

Thanks in advance for any info, it's always appreciated.

edit: oh, and my dad was saying that this doesn't apply to his cams because they are hydraulic, I didn't think he was right about that though.

 

[FastSUV]

ON STOCK motors with flat tappet cams, SM oils are fine...especially if they are already broken in and have some miles on them...it is true that SL oils generally have more ZDDP but again, most stock flat-tappet motors have weak valve springs & hydraulic lifters so there is not enough pressure to wear down a cam lobe.

Some standard SL oils are still out there but rare, and some of the HM oils available are still SL rated. So if you fit into the categories I mention then you are fine to use an SM oil, although a HM oil would generally be a better choice for an older motor anyway whether it is SL or SM rated regardless.

On a new/rebuilt flat-tappet motor, a HM oil or Rotella 15w40 is a good break-in choice, but it is the race motors with high-pressure valve springs or solid lifters that this ZDDP/moly thing become paramount

 

[BuickGN]

You guys can't keep going around and saying people will be fine on stock flat tappet engines on SM oils. It's more likely than not that they will be fine but that's not always the case.

In the Turbo Regal world, it's one of the larger collection of fast cars that still use flat tappets. Many of the old stock valvesprings that are pulled out measure 65lbs. The stock cam is something like 192/196 with very low lift and slow ramp speeds. Even so, we saw a much larger than normal cam failure rate when the change took place. Some were unaffected but there was no ignoring the extra failures. This is an engine with a 5,250rpm stock rev limiter.

IMO, there is absolutely no reason to play the odds. Use an oil with the correct amount of ZDDP.

 

[conradcliff]

Wow, thanks for the replies!

I love that I got view points from both sides of the spectrum.

Is there a zddp additive that would be good to use in SM oils?

 

[soldierman]

GM made or possibly still makes an additive called EOS I think that had quite a bit of zddp. possibly worth looking into.

 

[Chris71]

STP and Valvoline Synpower Oil Treatment

 

[m37charlie]

There are 2 fairly pure ZDDP additives I know you can get.
ZDDPlus 71800ppm Zn 51500ppm P 4 oz bottle
Redline Breakin 20000ppm Zn 17000ppm P 16 oz bottle

DO NOT add an entire bottle to a car sized pan 4-6 qts.
30ml of ZDDPlus will raise 5qts ~450ppm Zn ~310ppm P
4oz of Redline will raise 5qts ~500ppm Zn ~425ppm P

Over 2000ppm Zn can cause catastrophic chunking of cam lobes. Most SM oils are 600-800 P, 7-900 Zn. The new CJ-4 diesel oils still have 1100-1200ppm P, 12-1300ppm Zn, more than enough IMHO.

I'm not necessarily advocating their use, just if you do use the correct amount.

Charlie

 

[JohnBrowning]

I think you shouldgo with a good SM GF3 to get the better base stock technology and use addiives to bring up the ZDDP. The alternative is to use 15W40 or 5W40 designed for diesel engines!

 

[ARCOgraphite]

Folks are afraid to run Garden tractor oil, Like brigss and Stratton or John Deere 50. SH and SL. These are strong oils and have plenty of zddp and should be fine in a classic muscle car. Remember this stuff gets "used up" so if you run an SM just change earlier with a high velocity cam ramp. Valvoline and others make street "race oils" and most fleet oils have plenty of zinc. No need to pay $$$ for a high zddp oil - this additive is cheap. Alternatively, Motocycle oils with the SH/SJ will do the trick too. Also SM in a 10w40 typ does not follow the additisation req. of the "economy oils" and will have more zinc. As you see, there are all kinds of alternatives to current OTC SM - no need to freak out

 

[Pablo]

Some light reading material:

Amsoil TSB

 

[mikeyoilnutt]

Thanks Pablo. Very good information.

 

[ARCOgraphite]

Good show, Pablo. now I can point to this TSB instead of recommending Briggs and Stratton SJ API 30 oil!

 

[mechtech2]

conrad - Tell your father [nicely] that it doesn't matter if the cams are hydraulic or not, concerning wear. It is a total non issue.
Cams wore on older flat tappet pushrod engines no matter what. A little to a lot.
This is with the supposed 'good' oil.
So we can't blame perceived wear on new oil formulations.
What else should we expect from the most highly loaded/stressed contact areas in an engine?

Like mentioned, break in is a huge consideration.
I heard a guest oil engineer on a car show talk about this issue, and he said that after a proper break in, modern oil would be fine. High performance was another story - this was for the vast majority of stock systems.

Look at the success of modern flat tappet cams. Overhead cam engines are usually flat tappet bucket type, and wear is not a problem. This is helped because of lighter springs and smaller masses involved.

 

[Chris142]

FWIW my 4.0L Jeep has flat tappits and I'm not taking any chances with it. It HAS to get me to work.

I'm running the proper amount of ZDDP either by using addatives or finding oils that still have plenty of it.

 

[BuickGN]

Originally Posted By: mechtech2
conrad - Tell your father [nicely] that it doesn't matter if the cams are hydraulic or not, concerning wear. It is a total non issue.
Cams wore on older flat tappet pushrod engines no matter what. A little to a lot.
This is with the supposed 'good' oil.
So we can't blame perceived wear on new oil formulations.
What else should we expect from the most highly loaded/stressed contact areas in an engine?

Like mentioned, break in is a huge consideration.
I heard a guest oil engineer on a car show talk about this issue, and he said that after a proper break in, modern oil would be fine. High performance was another story - this was for the vast majority of stock systems.

Look at the success of modern flat tappet cams. Overhead cam engines are usually flat tappet bucket type, and wear is not a problem. This is helped because of lighter springs and smaller masses involved.


Spring pressures are much lighter in most OHC engines and the lifters and cam lobes are usually much wider. There's less weight to accelerate on top of that. You can't really compare these to older pushrod engines.

Typically the solid cams are a bit more aggressive than hydraulic cams with both being flat tappet.

 

[FastSUV]

Well I have 4.0L Jeep and have been unsing HM oils which have adequate moly & ZDDP, but I have stocked some regular SM dino oil too (Havoline being one brand). Is everyone now going against the weak valve spring theory?

I suppose it would be helpful to know what he has & how many miles. I mean on a '75 Chevy pickup then sure, use an HDEO or something, but on a modern vehicle with perhaps multiple cats & O2 sensors, we need to at least let it be known to conrad that if an engine uses any oil, that over time the extra ZDDP can poison the O2's & cats. I believe that is part of the reason SM oils were created is it not?

 

[BuickGN]

I'm not going against it. I don't know the numbers but I would say you have a good chance of nothing happening on a broken in stock engine. However, as a community (Grand National) there have been higher than average failure rates with stock engines and SM oil. If you were to play the odds, you would likely win but why take the chance when it's as simple as buying the right stuff?

 

[FastSUV]

well those turbos tend to cook oil and raise combustion pressure so those two effects (fatigued oil & more force on engine parts) on a grand national might be enough to psuh SM dino over the top & cause failures but on a stock "tractor motor" that sees low HP & low RPM's I'd think the SM would be fine on a broken-in motor (as you stated)

 

[BuickGN]

The GNs only spin about 4,900rpm with a 5,250 limiter in stock form. Oil temps aren't bad in the stock cars, they come with an oil cooler. It may get sheered in the rings and bearings a little more, I'll give you that. But boost takes some of the pressure off the intake lobes.

 

[1999nick]

If an SL oil promotes longevity in a high performance flat-tappet engine, wouldn't it also provide the same longevity benefit in all engines? That theory is why I use Mobil 1 10W30 High Mileage oil in my 2005 Nissan Pathfinder, even tho it presently has only 42,600 miles on it. I may try the newly available 5W30 M1 HM for my next oil change. The Pathfinder manual specifies SL formulation, and either 5W30, 10W30, or 10W40 weights, with 5W30 being the preferred weight. All of the M1 HM weights are SL.