ZDDP has NOT been removed from oil. I has been reduced to 'nominal maximum' of 800 ppm in the SM-GF4 spec oils listed as 'Energy conserving'.
The problems I am aware of mainly deals with flat tappet cam pushrod engines. Many people are reporting early cam/ lifter failures...but then there's the issue of the influx of Chinese made 'offshore' lifters and other metallurgical issues, changes to valve train geometry, not to mention high lift cams and valve spring pressures many people use now in 'musclecars'.
An OHC design as a rule produces less stress on the lifter face than a flat tappet pushrod design also. Without making this too long, while the issue is much debated, oil manufacturers have always succeeded so far in making oils 'backwards compatible'. The story some promote that the 'new oil' takes no consideration for older engines is flat wrong.
For most stock engines after break in under normal conditions I think it's much like the 'you must install hardened exhaust seats' myth.....for all the people who quote this and say they know it's absolutely true you can find equal numbers who have been running on unleaded for decades in a wide variety of engines with no problems.
Actually in the old days (contrary to popular conception now) high lift cams often failed early. The OEM factory cams often were phosphated and the factory lifters often had a special hardened foot on them (speaking of flat tappet pushrod cams here). There are a lot of variables here and the 'new oil' is the easiest target to find.
Keep in mind when people speak of 'British car problems'...how many are thinking of problems proven in the Triumph 2 liter OHC engine?
Probably about ZERO!
http://www.allpar.com/old/oils.php
"I talked with the OEMs in Detroit. The API SM IILSAC GF-4 engine oils should be suitable for older engines with flat fappets. The specification testing for oils with this performance category includes two engine wear tests (Seq. IIIG and Seq. IV) which use engines with flat tappets. Both the Seq. IIiG (GM engine) and Seq. IV (Nissan engine) are flat tappet engine tests measuring wear. For an oil to meet the specification these wear and scuffing tests must be passed. You will remember that API SM/GF-4 engine oils have a phosphorus limit of 0.06% min. and 0.08% max. It is also important to use the recommended viscosity grade (e.g. SAE 10W-30, SAE 10W-40).
An alternate suggestion is for those who are not convinced they may wish to use oils meeting the new API CJ-4. Although designed for diesel engines it has lower ash levels. Phosphorus levels are as much as 0.12%. API CJ-4 engine oils should be showing up in stores shortly. It may be possible to find these oils in SAE 10W-30 as well as the [other grades]."
