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Caterpillar Lubricant Test Engines

Sooty Jim

Researching for an article and thought I'd hit up the soot-head brain trust to see what they might have in their files.

See the image below. No doubt you have seen Jim Rush's Cat oil test engine displayed at Portland and pics of it online. That engine is the subject of the story and also to cover the development of diesel rated lubricants, specifically DELO (Diesel Engine Lubricating Oil). Jim has very little info on his engine or the type generally.

What I have been able to determine so far is that it's a single cylinder of the D13000 engine, 5.75x8" B&S. A research engineer from Standard Oil Company, George Neely, who teamed up with Art Rosen's research department at Cat to develop the legendary RPM DELO lubricant line, states Rosen was already using an engine with that B&S in the '33-35 timeframe (he is not specific about the exact year) which is near the time the D13000 debuted. Many reports show the 5.75x8" test engine (I can find no references to a model designation but Jim says it was called a "1D") was certainly around in the late '30s, through the '40s and into the early '50s when the 1Y73 test engine debuted ('50 is stated elsewhere for the 1Y73 debut but I have not verified that).

I have reached out to my sources at Cat but they have been slow to respond. I have also reached out to Chevron but some of you guys may also have some valuable clues. I know these engines have been discussed several times on the board and I was able to glean a few odds and ends from them. These lube test engines seem to operate under the radar and are not listed in any of the Cat catalogs I can find. I did find one recent brochure from listing part numbers for some of the most recent test engines but that's about it.



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Hi, only have a minute, Mobil had 7 of them in the Paulsboro nj lab, they ran and were started by dynos. I remember 1y’s I think before that it was 1g. Very hard to get parts for 20 years ago, most were custom made in small batches for Cat. There is a previous thread somewhere here on them. I believe some refer to them as scotes. There’s one around the corner from me home made hooked to a generator. I believe it is for sale


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I remember an article in the ACMOC magazine on those engines a few years back. I have no idea what year or issue, now...you might put a post on the ACMOC bulletin board, somebody on there will have some info.


I work in a lube testing lab that just removed one of these. Ours went to Intertek in San Antonio (I tried to scrounge it, but no dice). Ours was a CAT 1y73, I believe, also known as SCOTE, single cylinder oil test engine. I googled an ASTM test and here's what popped up for it --> https://www.astm.org/DIGITAL_LIBRARY/STP/SOURCE_PAGES/STP509A2B_foreword.pdf

I'll check around tomorrow and see if this is the correct astm spec and engine model number.


Sooty Jim

Thanks for the help so far Stack-heads.

I've learned quite a lot since I first posted.

The 1Y73 is the second series of SCOTE and debuted around 1950. It's still in limited use but probably won't be much longer because it's such an antiquated design and tests derived from it have few, if any, application to the modern world of diesel lubrication. It has a 5.12x6.5" B&S. The 1Y73 is essentially a single cylinder from a D337 engine (and the other derivatives in the same engine family with the same B&S). I found that same ASTM PDF early in my research and wish it was the entire booklet.

Rush's engine is a generation earlier than the 1Y73 and the general types like them date back to 1934 for sure and probably earlier ('33 is likely and '32 is possible). As mentioned, it's a derivative of the D13000 (and all the other similar engines with different designations and a 5.75x8" B&S). I found references to the 5.75X8" engines dating back that far, some directly from Art Rosen (research engineer at Cat) and his counterpart George Neely at Standard Oil.

Those two men worked closely together in solving the lubricant issues faced by the industry. My article will present a lot of detail on the lubricant problems and how they were solved. Rosen and Neely probably led the way for the rest of the engine and lubricant industry in demonstrating the efficacy of using lubricant test engines. Chevron sent some material showing the 5.75X8" engines in their labs as early as 1937 and Neely noted they had on in the Standard Oil lab in 1934. Prior to this time, Standard oil did most of their testing in the lab, but had brought in a few Model T engines in around 1925 to develop an oil to solve the wet clutch chattering issues. Tests done during that development gave Neely a quick start on the Cat issues.

I'm kind of an oil nerd but certainly not a chemist, so I had to look a lot of stuff up and it really made my brain hurt. Ah, yes, exciting days in the lab for Neely, mixing up aluminum di-naphthenate and stearic acid into a mineral base oil and then discovering calcium cetyl phenate was better than stearic acid. Neely's papers showed quite a bit of excitement over this stuff!

Cat Historical wasn't much help in this instance and the archivist stated he didn't remember anything on SCOTE engines in the files. I found several SAE papers from the period and some of the principals which detail many aspects of this. Chevron (formerly Standard Oil) was helpful from the lubricant side of things.

The one question I would REALLY like to nail down is the designation(s) for the early 5.75 x 8" B&S test engine. Rush has limited paperwork but says the only designation he's seen is "1D". His is likely from the '40s. I was hoping to track the development and evolution of the Cat SCOTE, especially that first-gen, but since Cat has not come thru with any info, and I am rapidly running out of deadline, I may have to run with what I have. I have enough to tell the story of how the development of diesel technology was stalled in the early '30s until the lubricant industry caught up, but I hoped for more detail on the "1D" first-gen SCOTE.


Jim I believe the first engines of the 5 3/4 x 8 design were 5 1/4 x 8 used mostly in the numbered diesel crawlers (35, 50, 75,) but also offered as power units. The 5 3/4 x 8 engines were added about 1936 when the RD tractors replaced the numbered diesels. The RD line (RD6, RD7, RD8,) changed to the D6,D7, D8 in 1939 I think. Both the 5 3/4 bore and the 5 1/4 bore engines were offered into the 40's. The 5 1/4 bore engines were: 3 cyl d 5500, 4 cyl D7700, 6 cyl D11000
5 3/4 bore engines were: 3 cyl D6600, 4 cyl D8800, 6 cyl D13000 and of course the v-8 D17000
I think the first numbers of the models were approximate horsepower.
By 1939 some smaller bore engines were in the line and I think the original Diesel 4 cyl which was not at all like any of the other engines to follow-about 1 year production, maybe around 160 made in 1932, were 4 cyl 6 1/8 x 9 1/4. See one of these running on you tube with a search for: 1932 caterpillar diesel 60/65. these engines were rated 65 HP but the tractor was a normal 60 (gasoline).

eddie bedwell

Hi Team,
to the best of my knowledge the 5500 (5500G) was a Gas engine.
From My Cat Rack Setting Book the 5 1/4 " bore x 8" stroke 3 cylinder Diesel was known as a 6100, 4C 9001-up S/No in Industrial Applications and 6F0001-up in Power Unit Applications.

The D9900 was the designation for the 6 1/8" Bore x 9 1/4" Stroke 4 cylinder Diesel used in the Diesel 60/65, 1C 0001-1C 0157, and the Diesel 70, S/No 3E 0001- 3E 0051 Tractors.
In Industrial Applications it had a 4C 3001 to 3150 S/No range as said above.

I have had the privilege of working on the fuel system and governor of one of these beasts that had intrigued me since I first heard about them as an Apprentice at the local Cat Dealer.

George Logue's old Diesel 60 was imported here to Australia but ran poorly due to retarded Injection timing and worn governor parts. It now runs sweet except that now the previously repaired starter motor (pony) pinion housing misaligned repair caused the starter pinion shaft to fracture--new one being made and the pinion housing has been bored and sleeved true.

Cat made a glass cylinder for one of the older CRC-L1 Test engines, long with a write up on the first D9900 built in 1930 being retested and passing the 1975 California Emission Standards--I hope I can post a scan of some pictures and dialogue again as I think we cannot re-post previous pix again.

Hope this helps.
Eddie B.


Sooty Jim

It helps and it makes me take a step back in one area... the CRC-L1 designation. This far I have see the following designations; 1D, 1Y73, 1Y540 and 1Y3700. While the article will mostly concern the first generation oil test engines, I plan to round up the descendants as well.

RE enginenut2's point, Both Rosen and Neeley clearly stated 5.75 x 8 inch test engines in those early days and that B&S may predate the production engines with those dimensions. It's not beyond possibility they were in error and meant to say 5.25 x 8, but I'm not going to second guess their statements without more information. It seems likely that the updated engine was in development and Rosen used the new B&S dimensions for the engines. Also possible that there was a mix of the 5.25 and 5.75 bore engines and only the 5.75 was mentions. This may become clearer as more documentation arrives. When the deadline arrives in the near future, I will go with the best available information and try to make it clear the info is not engraved in stone yet. The journalistic punt!