LT-5 Oil Question Delo 400 ZDDP

[Terry M.]

Re: Hey Duke

With a ZR1 one needs TWO catalytic converters. Two are also required for 1992-96 LT1/LT4. One does not want to need any of these. Among other things, they are long-since GM-discontinued.

I don't wish to take this thread off topic, but I have to wonder why the LT1 in a Corvette requires TWO converters, but basically the same engine in a Caprice/Impala SS requires only ONE converter. On top of that the pre-1996 OBD 1 system does not measure Catalytic efficiency so the efficacy of the converter in these OBD1 systems is not an issue.

Again my apologizes for an off-topic question.

[Joe L.]

Re: Hey Duke

I don't wish to take this thread off topic, but I have to wonder why the LT1 in a Corvette requires TWO converters, but basically the same engine in a Caprice/Impala SS requires only ONE converter. On top of that the pre-1996 OBD 1 system does not measure Catalytic efficiency so the efficacy of the converter in these OBD1 systems is not an issue.

Again my apologizes for an off-topic question.

Terry------


I believe the Gen II small blocks installed in the "B" bodies were rated at a lower horsepower than the Corvette LT1. The single converter may have been part of the reason. I believe the horsepower rating for the Impala SS was 260 versus 300 for the Corvette LT1.

OBD I does not measure catalytic converter efficiency. However, smog checks required in many areas of the country do measure HC, CO, and NOx emissions. A failed converter(s) will result in test failure.

[Duke W.]

Re: Hey Duke

There is evidence that organ-metallic compounds like ZDDP degrade catalyst performance over the miles, which is why manufactures via the API agreed to reduce the P concentration in S-category oils about ten years ago due to increased miles EPA mandated emission control system warranties. This was also accompanied by "roller everything" valve train designs.

But you have to balance the above issue with how many miles are on the vehicle currently, how quickly miles are being accumulated, and whether or not the vehicle is required to have periodic field emission tests. Many states exempt cars over 25 years old or more, and some have "collector car" plates that don't require field emission testing.

So it comes down to the individual situation - car, owner driving habits, and legal jurisdiction.

Back in the eighties/nineties many cars had two catalysts for each exhaust bank, so 4 for a V8. The first catalyst was "closely coupled" meaning that it was attached directly to the exhaust manifold or very close. These were usually oxidizing only cats that would "light off" quickly to reduce HC and CO. This would also heat up the second three-way cat more quickly, so full emission control would be effective within about two minutes of engine start during the EPA test with the cold start done at about 70F ambient.

Also, during the warmup air injection is used which helps the primary cat oxidation process, which shortens the time to go into closed loop operation and full emission control, and these pumps are now electrically driving, like on late model Corvettes.

During the EPA emission certification test, which takes about 45 minutes, including a "hot soak" of something like 10 or 15 minutes, about 80 percent of total emissions are created during the first couple of minutes of engine operation before it's warm enough to go into closed loop operation, so it's very important for designs to heat up the cats rapidly in order to minimize the time for the system to achieve closed loop operation and full emission control.

I think most recent model cars have just one three-way cat per exhaust bank, but some heavier cars may still have two. Emission cut points are absolute in grams/mile, so a light car with a small engine can have higher proportional emissions than a heavy car with a large engine.

Duke

[Terry M.]

Re: Hey Duke

Terry------


I believe the Gen II small blocks installed in the "B" bodies were rated at a lower horsepower than the Corvette LT1. The single converter may have been part of the reason. I believe the horsepower rating for the Impala SS was 260 versus 300 for the Corvette LT1.

OBD I does not measure catalytic converter efficiency. However, smog checks required in many areas of the country do measure HC, CO, and NOx emissions. A failed converter(s) will result in test failure.

Joe
Yes, the B/D-body Gen II LT1 is rated at a lower HP than Y-body LT1. The heads are iron in the full size cars, and the jury is still out on which flow better. Given the age of these motors I doubt a definitive conclusion will ever be reached on that issue. Since it has been Chevrolet's practice to rate engine power highest in Corvette (except for 1970) I have always taken all the engine HP numbers with a large grain of salt. Those numbers only mean what Chevrolet wants them to mean.

Each attainment district has different rules regarding emission testing these older vehicles, so as you and Duke say it boils down to what one can do in each situation.

FWIW in Illinois there is no emissions testing for OBD1 or non-OBD vehicles. The rational is that there are so few of these vehicles on the road it is not cost effective to maintain the testing facilities required to measure their emissions. So far in my lifetime this is the first good thing I have found about rust. There has never been roadside testing in Illinois, to the best of my knowledge.

[Dick W.]

Re: Hey Duke

Patrick------


Yes, high zinc and phosphorous oils DO have a detrimental effect on catalytic converters. That's the primary reason that zinc and phosphorous levels have been reduced in gasoline engine motor oils.

Personally, I would NEVER use a high zinc/phosphorous motor oil in a car with a catalytic converter. Also, I would NEVER use a diesel oil, even ones dual rated for gasoline use, in a vehicle with a catalytic converter.

Have you ever priced an OEM catalytic converter? If so, you'll be even more convinced.

My '94 Park Avenue still has the original converter and has had CJ-4 or the previous designation diesel oil in it since new. No problems what so ever. I have run that in everything other than the 2011 Yukon which requires Dexos, since the early '60's without any converter problems.

[Joe L.]

Re: Hey Duke

My '94 Park Avenue still has the original converter and has had CJ-4 or the previous designation diesel oil in it since new. No problems what so ever. I have run that in everything other than the 2011 Yukon which requires Dexos, since the early '60's without any converter problems.

Dick-------


Does the Park Avenue undergo periodic emissions testing?

[Mark E.]

Re: Hey Duke

I don't wish to take this thread off topic, but I have to wonder why the LT1 in a Corvette requires TWO converters, but basically the same engine in a Caprice/Impala SS requires only ONE converter. On top of that the pre-1996 OBD 1 system does not measure Catalytic efficiency so the efficacy of the converter in these OBD1 systems is not an issue.

Again my apologizes for an off-topic question.

Aren't multiple converters used to improve exhaust flow/reduce back pressure?
Corvette HP dropped almost 20% in 1975. I believe a lot of this is caused by running the exhaust through a single converter.

[Terry M.]

Re: Hey Duke

Aren't multiple converters used to improve exhaust flow/reduce back pressure?
Corvette HP dropped almost 20% in 1975. I believe a lot of this is caused by running the exhaust through a single converter.

That sounds counter-intuitive, but that means little in the real world.

[Dick W.]

Re: Hey Duke

Dick-------


Does the Park Avenue undergo periodic emissions testing?

Yup for the past several years. It will not have to pass another as NC, with EPA's blessing, dropped emissions testing for our county

[Duke W.]

Re: Hey Duke

Nope... the reasons are as I explained in post #18.

The early "bead bed" GM converter was extremely restrictive, and with only one, that's why the '75 Corvette base engine was rated at only 165 SAE net HP, which is the lowest net HP rated Corvette engine ever produced. Modern monolithic (honeycomb) converters offer much less backpressure.

Duke