No Repower - Rebuilding Mid-Season

Why in your particular case is the oil is your light but severe use. If you were a commercial guy running the engine 8 hrs or more every day... then the Delo 100 30 wt.

That is the correct recommendation. Detroits are hugely reliable engines and last a long time. But your situation is hard because of the intermittent use. Like you should change oil before you put the boat away (like for the winter) and not after first startup in the spring if your climate is such. My point is you really are outside the normal for what the engines were intended in operation but my opinion is just that. Have not ever owned a Detroit and only 4 strokes. Also, use of a marine oil is not bad idea either. Cat has there own oil but I have used the Delo 400+ without problem.

Like I say it is my opinion and your engine...

Couldn't get to sleep... so called a friend in California with 50 years experience in engine development and engineering... evening there good time to get ahold of him.

Well I got the low down on DD two strokes and why the cylinder ring problems. It was explained that in a 4 stroke engine the cylinders have pretty constant temperature control (cooling jacket is over most of the cylinder surface provides little temperature gradient over the entire cylinder. DD two strokes do not as the ports take up a significant part of the cylinder and the cooling jacket it on the top of the cylinder. So there is a temperature gradient over the cylinder that is not present in a normal 4 stroke. This is mad worse by the charge air entering at the bottom of the cylinder. It is best to run the engines on the cooler end of the spectrum and maintain the cooling system... easy to kill the o-ring seals on the cylinder. Also, the DD two stroke has the problem of the rings traveling over the ports this result in marginal lubrication conditions outside of operating temperature of the rings and liners, and is aggravated by the ability barrier of the ports to allowing oil circulation up the cylinder resulting in low lube conditions of the cylinder liner and rings. This is why they recommend the 40wt oil because the oil is heavily burdened on these engines on the cylinder liners. If you have good cooling and cooling system is well maintained the oil situation in the cylinder liner and rings is marginal. This is aggravated particularly in the turbo engines and marine applications because the charge boxes tend to accumulate condensation due to the very high scavenge ratios and design of the charge system and boxes. On your turbo engine the most critical maintenance is to make sure the automatic check valves draining condensation from the charge boxes is vital. Also, this high rate of scavenge results and them moisture issue results in further stress to the oil film on the cylinder liners and rings. ALL OF THESE result in higher scuff conditions for DD two strokes and it all combines to result in the lowered lube conditions of the cylinders and rings compared to 4 strokes.... and why the 40 wt is recommended, and the primary limiting factor in DD 2 stroke engine life. But they are cheap to fix!

Also, the cam and cam followers wear excessively with lighter weight oil supposedly.

He recommends you ONLY use the MARINE OILS... such as Delo 1000 or Delo 710.
Here is all the data sheet from Chevron... click on the oil name... and data sheet pdf comes up. Check the sulfated ash limits on the oils and for the engines he said he knew the 149s had an ash limit but was unsure of the 92s there are other oils too (edited).
https://cglapps.chevron.com/msdspds/PDSPage.aspx?directPDSLink=true&language=en&region=NA&txtPDSNumber=DELO&lbLanguage=ENGLISH&lbCompany=UNITED STATES

He thinks you can use the multi-grade if the oil is more frequently changed or closely followed in analysis so it does not lose its viscosity stabilizer effectiveness... also the heavier synthetics like the 4o wt or 20-40 wt. DELO 710 may be a potential help.

He suggests you change oil often and do oil analysis. Also, check the condensation drains in the air charging system (inlet charge boxes) are working properly every time you use the boat. And, again use the MARINE versions of the oil which Delo has available.

Thanks long time... got to catch up with an old friend.

The gentleman actually got good service from his engine before it gave up the ghost. And, I am sure will keeping the drains in the inlet system working and drained of condensation and regular and good maintenance the engine will out life his use of the boat using the recommended oil.

However, he has what is considered a severe use scenario... as most recreational boats do. The DD 2 stroke does not like to be set around and occasionally run... worse run hard after long periods of non operation... all diesels old and new do not take well to this. The issue as to his use is it subjects the rings and cylinder lines and pistons to premature failure from scuffing... and the oil is contaminated with soot quicker in that usage. The use of a more modern oil may help this in my opinion... that is what you get on YF opinions.

Actually if I owned the boat I would use either (if you are limited to Chevron Oils) the Delo 400+ LE 15-40 Wt. as it is rated for the marine environment, and meets the >1% ash requirement. As a second choice I would use the 20-40 Wt. Del0 710LE marine oil. For this usage... if I owned the boat... I don't. NONE of these oils were available in the time frame of DD 2 strokes hayday.

But still the Delo100 40wt. is the factory oil recommendation. There is no warrantee in play here. If it was a modern 4 stroke emission controlled engine you can literally only use the recommended oil... and you have warrantee issues... so you hire the factory authorized service and let them worry.

Certainly in constant use scenarios like a generator... I think Jacques-Yves Cousteau got a 100,000 hours out of a DD 2 stroke generator on his famous ship Calypso... those engines go forever... and in that case I would definitely run the recommended 40 Wt. Delo 100 .... DD two strokes will actually run on their lube oil when they are worn off and darn hard to shut down. The injection system was primitive but in being so was robust and easy to repair inexpensively... many service personnel really like it. They all have the same 5 inch stroke (except the 149) and only differ in bore... They are old engines. But old engines can be long lived and give good service. So he was absolutely correct to not re-power. The other issue is the boat... by time the engines wear out now he will most likely have moved on.

In fact rcapps>>>
ALL THE BRANDS for the same rating have similar or practically identical specs. so it is what you prefer for the same spec. rating.

Actually, it is an interesting problem with old engines and oil because the engines often outlast... particularly with rebuild... the availability of the oil in use in the era of the engine. Oils seem to improve all the time. A Gardner can still be rebuilt and last forever... for example. The technician who does the prototype injection molding development in my 'hobby shop' restores old engines and some of those are old enough to have originally used hardly refined (basically heated and the various constituents ladled off like grease from grave) well head oil for lube... or sperm oil. What do you do in that case....

From Wikipedia
"Pennsylvania grade crude oil is thermally stable and has a high viscosity index. It is generally free of asphalt and has only trace amounts of sulfur and nitrogen. It is also high in paraffin and other waxes making it highly desirable for refinement into petroleum lubricants such as motor oil."


"Sperm oil is a waxy liquid obtained from sperm whales. It is a clear, yellowish liquid with a very faint odor. Sperm oil has a different composition from common whale oil. Although it is traditionally called an "oil", it is technically a liquid wax. It is composed of wax esters with a small proportion of triglycerides, an ester of an unsaturated fatty acid and a branched-chain fatty alcohol. It is a natural antioxidant and heat-transfer agent. Through catalytic reaction, it carries phosphorus and sulfur derivatives providing anti-wear and friction modification...
Prior to 1972, over 30 million pounds of Sperm Whale oil was used annually in lubricants because of its exceptional lubricity and heat stability. In 1972, the Sperm Whale was listed as an Endangered Species and the following year, the US Congress amended the Endangered Species Act, outlawing the killing of whales and the use of their oil. The loss of whale oil had a profound impact in the automotive industry, where for example, transmission failures rose from under 1 million in 1972 to over 8 million by 1975. Even today over 14 million transmissions fail each year in the US."

Yeah I don;'t know anyone with a DD that is running anything but 40wt. Shella Rotella or oil from DD.

If it ain't broke, don't fix it.

This reminds me of a funny story... my brother (I guess it was around 35 years ago) had this 31 foot long sail boat he could only get anchorage for without shore power... so he had a little mini Honda generator he used to keep the batteries charged and the fridge going... in three years he had what he estimated to be over 3000 hrs on that tiny generator.... when I visited.

He lived in USA California at the time and got that ARCO graphite oil to use in the thing. When I visited he was changing oil in the thing and the oil coming out looked the same as the new oil going in.... black...

But I was astounded at the longevity of that mini 300w generator... I don't remember how long it ran over all but he said he sold it a year later when he got rid of the boat... Now typically for him, as the thing looked cosmetically new, he said it was hardly used. It still ran well but he did change oil and do good maintenance and got a good price!

I would recommend the Detroit diesel oil from the dealer for 2 strokes, it really isn't even anymore expensive than Chevron.

EVERY D.D. guy I know uses the Detroit Diesel 40 weight oil from the dealer which is the same price as the Rotella and Chevron, and recommended by the manufacturer. The D.D. oil is made by Mobil. A large DD dealer down here (FDDA) told me they see a lot of ring wear with Rotella. I don't understand why everyone wants to use whichever oil and filters, other than the engine manufacturers, when the dealers are the same price. I could see it if you're stuck in St. Croix and that's the only oil and oil filters you can find. MAN oil is made by Mobil also. MAN makes CAT oil also.....see a trend here.....

I think you have been blowing your own trumpet so much you have got mixed up.

MAN an engine manufacturer do not and never have made the oil you find in the CAT Containers.

I meant to say Mobil makes CAT oil as well, simple typo.

I don't use Rotella anymore as I've seen it break down far too soon and in D.D. 2 cycles it would not make as much oil pressure after 50 hours of running time at cruise. You're welcome to pour whatever you want in your engines. I use what the manufacturer recommends and puts their name on, considering it's virtually the same price, why not?