LT-5 Oil Question Delo 400 ZDDP

[Perry M.]

I have an LT-5 motor in one of my cars that requires high ZDDP oil. On the ZR-1 forum, Amsoil AMO 10W-40 is their highly recommended oil almost exclusively. It is almost $12 per quart although I can get it for $10.50. It has 1265 ppm of phosphorus and 1378 ppm of zinc. It is not rated SG compatible ( it is rated SL, SJ, and SH for gasoline engines ) but then neither is my ample supply of Delo 400 LE 15W-40 ( rated CJ-4 ) oil that I use in my other cars. My question is this, can I use Delo 400 oil in my LT-5 motor without consequences? Your expertise is appreciated.

[Joseph L.]

Re: Hey Duke

The safety data sheet for Delo 400 LE says it has 0.1-2.5% Zinc alkyl dithiophosphate.

[Joe L.]

Re: Hey Duke

I have an LT-5 motor in one of my cars that requires high ZDDP oil. On the ZR-1 forum, Amsoil AMO 10W-40 is their highly recommended oil almost exclusively. It is almost $12 per quart although I can get it for $10.50. It has 1265 ppm of phosphorus and 1378 ppm of zinc. It is not rated SG compatible ( it is rated SL, SJ, and SH for gasoline engines ) but then neither is my ample supply of Delo 400 LE 15W-40 ( rated CJ-4 ) oil that I use in my other cars. My question is this, can I use Delo 400 oil in my LT-5 motor without consequences? Your expertise is appreciated.

Perry------


What makes you think that an LT5 engine requires high ZDDP oil?

[Perry M.]

Re: Hey Duke

Because, even though it is an overhead 4 cam engine, it does not have roller anything, The valves operate directly off the cam., flat surface on flat surface.

[Dick W.]

Re: Hey Duke

CJ or CK oil has more than enough ZDDP to meet the requirements of your engine.

[Joe L.]

Re: Hey Duke

Because, even though it is an overhead 4 cam engine, it does not have roller anything, The valves operate directly off the cam., flat surface on flat surface.

Perry------


GM never specified any special, high zinc oil for this engine, just an API SG oil. In fact, for the initial years they did not even specify a synthetic oil although LT1 engines required that. I believe that in 1994 or 1995, they did add a synthetic oil requirement.

It's OK to use a higher zinc diesel oil as Dick suggests although I would not use one unless it was dual-rated for gasoline engines.

Otherwise, if you need higher zinc for your "comfort level" you could use any current gasoline rated 10W-30 oil and add a few ounces of GM Engine Oil Supplement to each oil change. There's no need to use expensive "special" oils.

[Duke W.]

Re: Hey Duke

Have you read my oil article that was originally published in The Corvette Restorer, circa 2008? An updated version is on the Web. In that article I made it very clear that API C-category oil should be used in engines with any sliding surfaces in the valve train and stated all the whys and wherefores. I doesn't appear that the Amsoil has an API rating. I may be on the backside of the bottle, but I doubt it. The Delo 400LE 15W-40 CJ-4 is perfectly acceptable.

You should download the pdf and post it on your ZR-1 Web site. It sounds like they are drinking the expensive "boutique oil" Kool-Aid.

Recently I picked up a gallon of Walmart's Supertech 15W-40 C-category, which is still rated CJ-4. It was less than ten bucks - $9.65 as I recall. Often this product is out of stock at my local Walmart. It is usually the least expensive CJ-4, but if Delvac or Delo is on sale for a little less, that's what I buy.

Duke

[Perry M.]

Re: Hey Duke

Thanks to all of you. You have confirmed my belief that my supply of Delo 400 LE oil is perfectly OK to use in all of my cars. Duke, I finally read your article and am now informed. Thanks again.

[Patrick H.]

Re: Hey Duke

Does high ZDDP oil affect the catalysts? I had read that it does, and as such was not to be used in catalyst engines.

Patrick

[Joe L.]

Re: Hey Duke

Does high ZDDP oil affect the catalysts? I had read that it does, and as such was not to be used in catalyst engines.

Patrick

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.

[Patrick H.]

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.

That's exactly why I asked.

I'd hate to find a ZR-1 catalytic converter, much less replace one.

When the LT5 was built they specified Mobil1 oil. I find it hard to believe that 2018 vintage Mobil1 wouldn't be useful in these engines, especially since they meet DEXOS specifications which are a bit more stringent.

[Joe L.]

Re: Hey Duke

That's exactly why I asked.

I'd hate to find a ZR-1 catalytic converter, much less replace one.

When the LT5 was built they specified Mobil1 oil. I find it hard to believe that 2018 vintage Mobil1 wouldn't be useful in these engines, especially since they meet DEXOS specifications which are a bit more stringent.

Patrick------


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.

Also, the 1990 to at least 1992 ZR1 did not specifically require synthetic oil. I believe that spec was added sometime after 1992.

By the way, C5 catalytic converters are discontinued. C6 converters are still available for about $1,000 GM list each (2 required).

[Mark E.]

Re: Hey Duke

http://www.zr1specialist.com/HAT%20Web/articles/Modern%20Motor%20Oil%20and%20the%20LT5%20Engine.pdf

Google found this article about C4 LT5 oil requirements by Marc Haibeck. I don't know him, but looking at his website, it looks like he has a shop that specializes in the C4 LT5.

"Catalysts are affected by metallic additives in motor oil. The metallics can lower the efficiency of acatalyst through a process known as deactivation. The EPA has extended the government mandated catalyst life requirement to 80K miles. It is this requirement that runs contrary to the needs of the LT5. API SG oil uses zinc and phosphorus as EP (Extreme Pressure) anti-wear additives. The two additives are often referred to as a package designated as ZDDP. Phosphorus is the more detrimental of the two, and is being progressively reduced to address the catalyst deactivation issue.

Maximum phosphorus per the API standard:

SG.12% or 1200 ppm
SH .12% / 1200 ppm

SJ .10% / 1000 ppm

SL .10% / 1000 ppm

SM .08% / 800 ppm


Zinc has been reduced in proportion to phosphorus within the ZDDP package, typically:

SG.13% or 1300 ppm
SH .13% / 1300 ppm

SJ .11% / 1100 ppm

SL .11% / 1100 ppm
SM .09% / 900 pp"


He goes on to recommend Mobil 1 High Mileage and Amsoil AMO 10W-40 Synthetic Premium Protection, which have these levels of P/Zn. As the OP mentions, Amsoil is the more expensive choice.

In the late '90s, I owned a 1990 ZR-1 and used Mobil 1. As Joe states, I believe this oil was recommended by GM for the last few years of this engine. Marc's point is the "regular" formulations of Mobil 1 have changed since then, with lower levels of P and Zn.

It seems the trick is to find the "Goldilocks" oil with enough ZDDP for the cam, but not too much for the catalysts.

[Perry M.]

Re: Hey Duke

That is the article in my original post that I was referring to on the ZR-1.net forum. My LT-5 motor is in a 67 Camaro that I've been building over the last decade. I'm not running catalytic converters so that is not an issue.

[Patrick H.]

Re: Hey Duke

There's an extensive thread on CF from 2010 that argues against much of what Marc says on his site.
I found it quite informative.

I'd like to know if there is a ZR-1 (LT5) engine that has failed due to the cam/follower issue that they allege may occur.
I hear far more stories about them going for tens of thousands of miles with zero issues than I do about failure, but I don't own one or specifically follow them.