Why higher iron wear with some makes

[Plawan]

What is it that leads some engine makes to have more iron wear in UOAs?
Is it different metals used in camshafts or cylinder walls?
I’ve noticed my rams Hemi and wife’s 3.6 pentastar produce higher iron wear metals in UOA than our toyota and Mazdas.
Also the old Yukon with vortec seems like it just can’t die yet produces way higher iron numbers.
Seems like less iron wear is better but like with the ole Yukon it hasn’t seemed to kill it.

 

[Kira]

Do the higher iron wear numbers amount to anything?

 

[Danh]

Lots of non-oil related reasons: engine displacement, sump size, camshaft drive type (belt vs chain) and length, and the list goes on.

 

[Plawan]

Do the higher iron wear numbers amount to anything?

I don’t know.

 

[OVERKILL]

Think of the potential sources of iron:
- Bores - if it is an iron block, or an aluminum block with iron sleeves
- Camshaft
- Lifters
- Rockers
- Rings
- Timing chain and gears

The iron block pushrod V8's all seem to produce higher iron. Some of this may also be due to swept ring area, due to displacement. It doesn't appear to have any impact on longevity.

Doug Hillary used 100ppm as a condemnation limit for iron in his UOA's and the bores in those big old 550HP Detroit Diesels still looked like new and were within factory new spec at 1.2 million km. I wouldn't worry too much about it.

 

[RDY4WAR]

Oil sump capacity relative to engine size is a consideration. Both my Mustang and my Tahoe take 6 quarts of oil though one is a 3.7L V6 and the other a 5.3L V8.

 

[FTTSHO]

It seems most pushrod OHV engines generally have higher wear metals on UOA’s, compared to a lot of OHC engines. I think we can kind of all agree on this.

Pushrod engines have more valvetrain friction by design. That’s the reason why we generally see higher wear ppm in general with pushrod engines. With pushrod designs, there are more metal on metal contact that can happen, especially in the valvetrain part of an ohv engine. Of course, oil does its job in keeping everything separated, but during the course of an oci, you’ll see more wear on engines that inherently have higher friction. No oil can prevent this. However, better engine design can lower wear metals.

A lot of modern engines have OHC or DOHC with lifter buckets, which has less valvetrain friction, but it all really depends on all the different designs by all the different car manufacturers. Some ohc engine do have more wear metals than some ohv engines. Why? It’s just how some engines are.

But higher ppm of whatever metal on a UOA doesn’t mean the engine won’t last as long as some other engine that doesn’t produce as much wear particles with the same miles on the oil. We are talking about ppm, which stands for parts per million.

Just keep up on oil changes, use a good filter, and there’s nothing to worry about.