Diesel Oil

[Roger W.]

The February 2023 issue of "HOT ROD" Magazine has an article about using diesel oil with ZDDP in a gas engine. Diesel oil is not the same as gas oil. Diesel engines run at lower speeds than than gas engines so diesel oil does not have as much or the same type of ZDDP as Gas engine oil. Also diesel oil does not have as much anti foam additive as gas oil.
The article recomends contacting the oil companies and giving them the specifics of your applicaion such as street or race use and bearing clearances and asking the oil company which oil to use.

[Duke W.]

Re: Diesel Oil

I haven't read the article, but from what I've heard from others it has a lot of nonsense.

Do yourself a favor and read my oil article to get a basic education on engine oil. It's here in the restoration data base documents sticky or just do a Web search:

"engine oil for vintage corvettes"

Include the quotes so it looks for the exact phrase, and it should be at the top of the list.


Duke

[Mark E.]

Re: Diesel Oil

Here's the article: https://www.motortrend.com/how-to/di...soline-engine/

Duke- What about it is nonsense?

I'm not a Petro Engineer but like the idea of using an oil formulated for spark engines and flat tappets. It's not that much more expensive than diesel oil; for example Mobil 1 15w-50 synthetic has 1200 PPM P and 1300 ppm Zn, and is about $26 for five quarts at Walmart.

[Thomas S.]

Re: Diesel Oil

Duke’s Reference. https://www.forums.ncrs.org/attachme...9&d=1499375245

Boils it down very well, and has links at the end for anyone wanting dig deeper into the subject.

[Duke W.]

Re: Diesel Oil

Here's the article: https://www.motortrend.com/how-to/di...soline-engine/

Duke- What about it is nonsense?

I'm not a Petro Engineer but like the idea of using an oil formulated for spark engines and flat tappets. It's not that much more expensive than diesel oil; for example Mobil 1 15w-50 synthetic has 1200 PPM P and 1300 ppm Zn, and is about $26 for five quarts at Walmart.

He claims that ZDDP for diesel engine oil is the different than for gasoline engine oil. I've been well aware of engine oil formulation for over 50 years and I've never heard that one before.

I'm not aware of any differences in the API C and S-category foaming tests, but I did run my Cosworth Vega in track events for 15 years accumulating something on the order of 5000-8000 mile hot lapping Riverside and Willow Springs courses usually shifting at 6500 and sometimes 7000 on a completely stock engine using 15W-40 C-category oil and never had any oil related problems.

The "violence" in the crankcase that can lead to foaming is more a function of mean piston speed than revs, and a six-inch stroke HD diesel engine governed at 1800 is making the same mean piston speed as a 302 at 3600. Also HD diesels have turbochargers that have very high bearing surface velocities, which places a premium on shear stability and anti-foaming properties.

Lake Speed Jr. has a financial interest in some boutique oils, though the article does not so state. I have NO financial interest in any engine oil products.

By now you should have enough information to make and informed decision.

Duke

[David M.]

Re: Diesel Oil

Just add this to what ever oil you choose to run and RUN IT.

I've disassembled stand-by large displacement 10 to 48+ liter generators used in prime power applications, read not designed for 24-7 running (middle finger to the utilities) exhibiting stand-by generator wear characteristics. So low to no wear.
I have disassembled several at or past 8000 hours of annual run time (this is prime power generator runtime territory) and the wear was negligible, As in zero main & rod bearing wear. Negligible valve train wear (lap in wear) to include cam lobes rocker push rod cups lifter faces etc.

You need to break in the engine before using Prolong.

The juice simply works. I have been running this additive for 25-30 years and before it its predecessor Slick 50. I have yet to blow up an engine. Everybody who knows me knows I'm not easy on my muscle cars. They deserve a beating, thats what they are for. The 442 has 35K harder or shall I say spirited driving & some track miles since a full tilt rebuild. Thats 30+ years of fun. Zero ticks knocks etc. Its a Timex.

Everyone really worries about this way more than necessary. A prime mover (large engine powering something) that runs 24-7 steady state load or a drag car running on the bitter edge of metallurgy needs to worry. Not a pampered gently driven garage queen. Run Wally World oil (which actually reviews well) with Prolong RELAX and sleep well.

[Terry M.]

Re: Diesel Oil

Just add this to what ever oil you choose to run and RUN IT.

I've disassembled stand-by large displacement 10 to 48+ liter generators used in prime power applications, read not designed for 24-7 running (middle finger to the utilities) exhibiting stand-by generator wear characteristics. So low to no wear.
I have disassembled several at or past 8000 hours of annual run time (this is prime power generator runtime territory) and the wear was negligible, As in zero main & rod bearing wear. Negligible valve train wear (lap in wear) to include cam lobes rocker push rod cups lifter faces etc.

You need to break in the engine before using Prolong.

The juice simply works. I have been running this additive for 25-30 years and before it its predecessor Slick 50. I have yet to blow up an engine. Everybody who knows me knows I'm not easy on my muscle cars. They deserve a beating, thats what they are for. The 442 has 35K harder or shall I say spirited driving & some track miles since a full tilt rebuild. Thats 30+ years of fun. Zero ticks knocks etc. Its a Timex.

Everyone really worries about this way more than necessary. A prime mover (large engine powering something) that runs 24-7 steady state load or a drag car running on the bitter edge of metallurgy needs to worry. Not a pampered gently driven garage queen. Run Wally World oil (which actually reviews well) with Prolong RELAX and sleep well.

David
No offense, but an engine (any engine) running 24/7 is a far different use than your 442 in "spirited" driving, or Corvettes that sit for months before a cold start (or a start from room temperature) and then are started three or four times (and run only at idle or barely above) before returning to their months or years-long slumber.

I am not disparaging the product you like so much; just pointing out the great differences in engine use.

Full disclosure: I once worked for a utility and currently work for a utility contractor, however my work has never been in generation or stationary power. And I didn't sleep in a Holiday Inn last night either.

[Gary C.]

Re: Diesel Oil

Duke,
I recommend you peruse the SAE technical paper series article number 2004-01-2986, titled “How Much ZDP is Enough?” by Robert M. Olree of General Motors Powertrain and Michael L. McMillan of General Motors Research & Development. And I did not mistakenly state ZDDP in the title, it is ZDP. This paper discusses that ZDP has different alcohols that make up ZDP, mainly aryl and alkyl. The alkyl version is commonly known as ZDDP. Alkyl alcohol used in ZDDP has four different styles that can be used including mixtures of each: Primary (short-chain & long-chain) and Secondary (short-chain & medium-chain). In this SAE paper, they describe that the aryl version was used initially in the 40’s since it was most thermally stable (less active) and generally better anti-oxidants, thus the reason automotive industry tried using it to solve the copper-lead bearing corrosion issues back then in the 40’s. However, the aryl style has worse wear characteristics as found out in the 70’s. Formulation has been adjusted throughout the decades including oils intended for diesel engines so differences between automotive and diesel are possible.

This paper also references many other SAE papers so I tend to believe these types of papers instead of the typical anecdotal evidence. When I presented a fuels & lubricants technical session at the 2021 Palm Springs NCRS National, I went over much of this SAE information from my research including bringing the 4” stack of SAE papers, probably a bit too technical for the audience but very interesting for myself.
Gary

[Duke W.]

Re: Diesel Oil

It sounds like you have done a lot of research, thus no need for me to reinvent the wheel.

So what's your conclusion: is API service category CK-4/SN the best choice for vintage gasoline engines with sliding surface valve trains and no catalytic converters, or should SN be used?

Duke

[Gary C.]

[William F.]

Re: Diesel Oil

One of the main advantages of using diesel oil in our vintage Corvettes which are often stored for months is the higher corrosion resistance of diesel oils as stated by an oil engineer in a 1999 Car and driver article which I have quoted in one of my previous posts. I'll stick with this and Duke's advice and continue to use the "heavy duty diesel" version (C only rated) Rotella T 10W30.

[Mark E.]

Re: Diesel Oil

...the latest Mobil 1 product data chart dated May 2022, they show a Mobil 1 Supercar 5W-50 that has an API SP approval, has a nominal phosphorus ppm of 1100 but is not catalytic converter compatible as identified by the PDS. Mobil’s data sheets at least show all the nominal phosphorus ppm levels for all of the listed oils and each person can refer to the PDS for more specifics.

I imagine this Mobil 1 Supercar 5W-50 would be too much cost for the vintage Corvette owner so a different oil such as the CK-4/SN would suffice for now.

I haven't seen Mobil 1 Supercar 5w-50. Do you mean Mobil 1 15w-50 which has 1200 PPM P and 1300 ppm Zn per their PDS? As I mentioned in an earlier post, it's about $26 for a five quart bottle.

[Duke W.]

Re: Diesel Oil

As stated in my oil article (2008, revised 2011) according to the API 1509 document, the P limit does not apply to S-category products with a winter SAE viscosity rating above 10W. That means that a 15W-50 or 20W-50 S-category product has no P limit, however, that DOES NOT mean that P is actually greater than 800 PPM.

You have to look at the spec sheet of the specific product to be sure.

Also keep in mind that new Boron-based anti-wear additives are now in use that reduce the amount of ZDDP necessary to pass the C-category wear tests, however, the boron content may not be listed. These new boron based anti-wear additives are likely patented or proprietary, and not a lot of information about them is on the Web.

Even if a C-category product has significantly less P than the 1200 ppm limit, it still has to pass the same C-category wear test, which is tougher than the S-category wear test, so it's likely that these products contain boron-based anti-wear additive in addition to the ZDDP.

Duke

[Mark E.]

Re: Diesel Oil

As stated in my oil article (2008, amended 2011) according to the API 1509 document, the P limit does not apply to S-category products with a winter SAE viscosity rating above 10W. That means that a 15W-50 S-category product has no P limit, however, that DOES NOT mean that P is actually greater than 800 PPM.

You have to look at the spec sheet of the specific product to be sure.

Duke

The numbers are from the Mobil 1™ Product Guide , not a "spec sheet" per se. Also, here's an excerpt from their brochure:

Screenshot 2023-01-10 112315.jpg

The footnote says "Zinc derives from ZDDP...", so I'm not sure what this actually means (Zn level? ZDDP level?)

[Duke W.]

Re: Diesel Oil

ZDDP is NOT measured in ppm.

Phosphorous is the surrogate for the amount of ZDDP, and for a given level of P, the Zn is usually in the range of 100-200 ppm greater. The concentrations of these elements are determined by subjecting the organo-metallic ZDDP compound to a spectrographic analysis.

If you read my oil article you should understand the above because I thoroughly explaining it.

But waaaaaaay too many guys keep asking/talking about ZDDP ppm, no matter what anyone does to educate them.

I believe the Mobil 15W-50 API primary service category is SN, and it can be so rated because the winter viscosity grade is above 10W as I explained in the oil article and again in this thread. The primary advantage of "synthetic" oil is longer service life due to the greater oxidation resistance of synthetic base stocks. This is why on some modern cars you can go 10-15K miles before the oil quality monitor recommends a change. Since typical vintage car usage is only a few hundred to maybe a few thousand mile per year, a time based change should be used, so you get no benefit from the longer miles service life, at about double the cost, of "synthetics".

Also, given that the 15W-50 Zn level is 1300 ppm, the P level is very likely in the range of 1100-1200, which is what most CK-4s are, assuming no Boron-based anti-wear additives, and the CK-4 P limit is 1200 ppm.

Be aware that most "racing oils" DO NOT have the detergents/dispersants required for long term road use in which case they DO NOT meet any API service category and should only be used in real racing engines that have oil changes at least after each race or every few hours of service, if not a complete teardown and inspection.

Duke