Pre-war (up to 1942) AMSOIL Z ROD 10W-30

[KenZ]

Anyone have any experience using subject oil with their Cadillac/LaSalle flatheads?  Thanks  KenZ

[z3skybolt]

Yes,

I have used it exclusively in both of my LaSalle, with a combined mileage of 17,000 miles.  My 5227 had a complete engine overhaul, everything inside new. It had a Cadillac 346 engine and was driven 10,000+ miles before being totaled in an accident.

My 5019 has the original 322 engine with an old overhaul done in 1984.  It has been driven just over 11,000(7,000 by me) miles since the overhaul.  Both engines operate fine with oil pressure in the low to mid 30s.

Happy with no concerns

Bob R.

[TJ Hopland]

I don't really know anything about these engines specifically but don't you go with something a little thicker for a typical used engine like this especially if its not going to be operated in cooler ambient conditions?

Is this one of the ones that has some brass gears where there is concerns about typical additives in todays oils?

[LaSalle5019]

Being a full synthetic, I wouldn't use it for break in but see no reason why it wouldn't be a good oil to use otherwise. Personally, I use dino oil since the engine has no filter and I change it pretty often so the cost gets a bit high using full synthetics.

[James Landi]

I'm all about using single viscosity 30 weight oil, as multigrades can cause extreme anxiety when your oil gauge slumps way down on hot days at idle. (I've known of several guys who had their engines rebuilt because of 'low pressure' at idle, only to experience the identical anxiety following the rebuild-- channeling the GM idiot lights) Yes, The Zinc additive is specially designed for flat tappet engines--where your cam lobes meet with extreme pressure from your tappets lifters.  The zinc formula in regular engine oil is bad for modern engines, thus the additive for old push rod engines. Valvoline has a special formula oil that includes zinc.

[KenZ]

Posed the question because I have a friend that uses the Amsoil Z Rod and strongly recommends it. Been using VR1 with no problems but it is not much of a detergent oil.  My 346 flathead has a recent rebuild with less than 3000 miles on it so changing over to a high quality synthetic detergent oil should be beneficial in the long run.  It is designed for older engines and has the required zinc. Yes, not cheap with cost being only drawback that I can tell. Thanks to all for your input.               

[Clewisiii]

Nothing really to add. I just like pictures.

[LaSalle5019]

No added ZDDP required in these engines. The added zinc wasn't even in oils when these pre-war engines were built. It was developed for the high performance aircraft engines that came about during WWII and then added to oils in the 1950s for the post-war modern car engines. The level in current oils is still plenty for most post-war engines except for high performance/race engines.  It won't hurt but I chose not to waste my money on specialty oils that aren't required.

As James Landi mentions above, I like to use a bit heavier weight oil in these engines for the reason he states. Or you can bump the idle rpm up a bit.

[Clewisiii]

I beleive the zinc is also for the missing Lead in the fuel.

[James Landi]

Like so many other additives, it's hard to know what is simply benign snake oil or  what products truly add performance and sustain the life to an  old  engine design.  Apparently, there are some tests that do, indeed, show cam lobe deterioration that folks claim was a result of the lack of zinc in new engine oils. I THINK Scott makes an important point worthy of emphasis... nothing works best to extend the life of an old engine than a user's CAREFUL management while driving and while maintaining an old car engine.   

[LaSalle5019]

I'll just add that I was an engineer at GM for 30 years, read all the SAE papers on ZDDP reduction (to help with catalytic converters), talked to the oil experts at GM and also one of GMs primary oil suppliers about this specific issue since I was an owner of several older cars. They (OEMs, oil suppliers within SAE) took the levels of zinc down to meet the needs of the exhaust treatment folks and ran all their standard engine tests to ensure backwards compatibility to the older flat tappet designs to ensure the zinc and phosphorus levels were still acceptable. They also tested higher levels which showed excessive bearing wear/spalling which is important too as people buying these ZDDP additives become the chemists and have no idea on the levels in their oil. All the oils today still have ZDDP, just at lower levels than back in the 70s 80s which all the SAE tests show are adequate for flat tappet cams on production OEM engines. Where it is recommended to go with a higher level is on performance engines with higher compression ratios, valve lifts and spring pressures - basically built performance engines. And you don't want to use additives, just buy the oil with the additive package designed by the manufacturer so you know what you are getting.

All this anecdotal and misinformation about "you need to buy our specialty oil for your flat tappet cam engine" started with the companies wanting to sell you something.

And again, a flathead Cadillac engine with its low compression, short valve lift and rather soft springs had no need for added zinc and ends up getting it anyway in the modern oils that are on the shelf.