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Marc Haibeck · 07-24-2011

The LT5 was designed for API SG oil. It is noted on the oil filler cap of the 1990 to 1992 engines. SG has .12% ZDDP. This is also specified as 1200 ppm ZDDP. Modern oils like Mobil 1 10W-30 have .08% ZDDP. They are removing ZDDP because it can reduce the efficiency of the catalytic converter. In the future they might remove more ZDDP.

This is a minor issue with the LT5 because the smaller valves have lower loads on the lifters. The LT5 load on the lifter at full lift is 248 lbs. The L98 with flat tappets has a lifter load of 375 lbs.

I have observed that the lifters wear more than the cams on the LT5. On the LT5 the main concern is lifter wear. Camshaft sprocket wear is also a factor. ZDDP is used to protect these parts.

The easy way to address this is to use an oil that is formulateded for older design engines with flat tappets. The Amsoil AMO product and many other products are available. These products have .12% ZDDP. Too much ZDDP can cause a problem too. The .12% level was used from about 1965 to about 1995 and is well proven.

Amsoil AMO is priced about the same as Mobil 1 if you sign up as a Preferred Customer. Since Amsoil AMO is a higher quality lubricant than Mobil 1 you could go an additional 1000 miles more than you would with Mobil 1.

If you want to save a few dollars you could use GM EOS as an additive for modern oil. About half a bottle of EOS will increase nine quarts of .08% ZDDP oil to about .12%.

If you are subject to emissions testing, modern oil might be right for you. Longer catalyst life might be as important and less lifter wear. Lifter wear due to reduced ZDDP seems to me to be a minor issue on the LT5.

07-24-2011	#6
Marc Haibeck Join Date: May 2007 Location: Addison IL Posts: 252	Re: Rizlone ZDDP additive The LT5 was designed for API SG oil. It is noted on the oil filler cap of the 1990 to 1992 engines. SG has .12% ZDDP. This is also specified as 1200 ppm ZDDP. Modern oils like Mobil 1 10W-30 have .08% ZDDP. They are removing ZDDP because it can reduce the efficiency of the catalytic converter. In the future they might remove more ZDDP. This is a minor issue with the LT5 because the smaller valves have lower loads on the lifters. The LT5 load on the lifter at full lift is 248 lbs. The L98 with flat tappets has a lifter load of 375 lbs. I have observed that the lifters wear more than the cams on the LT5. On the LT5 the main concern is lifter wear. Camshaft sprocket wear is also a factor. ZDDP is used to protect these parts. The easy way to address this is to use an oil that is formulateded for older design engines with flat tappets. The Amsoil AMO product and many other products are available. These products have .12% ZDDP. Too much ZDDP can cause a problem too. The .12% level was used from about 1965 to about 1995 and is well proven. Amsoil AMO is priced about the same as Mobil 1 if you sign up as a Preferred Customer. Since Amsoil AMO is a higher quality lubricant than Mobil 1 you could go an additional 1000 miles more than you would with Mobil 1. If you want to save a few dollars you could use GM EOS as an additive for modern oil. About half a bottle of EOS will increase nine quarts of .08% ZDDP oil to about .12%. If you are subject to emissions testing, modern oil might be right for you. Longer catalyst life might be as important and less lifter wear. Lifter wear due to reduced ZDDP seems to me to be a minor issue on the LT5.