Switching to Synthetic Oil, 8V71 MC-8

[Glennman]

1974 MCI MC-8 8V71 turbo. I'm thinking this would be a good time to fix some things at the oil pan where there are some pipe fittings and hoses that leak, as well as maybe replacing the pan gasket. The oil plug needs attention too (the plug and those pipe fittings are my main leakers at this point). While doing this, I will of course change the oil. I'm thinking of using a full synthetic oil in lieu of Delo 100. If this would be recommended, what kind of synthetic oil is equal to Delo 100, or what is the best synthetic oil for my 8V71 turbo Detroit? Any replies would be helpful. Thanks all, Glennman

[richard5933]

Does anyone even make a 30w synthetic which is certified for use in 2-stroke DD engine?

[chessie4905]

I'm pretty sure Ammsoil does, but due to normal oil consumption issues it was determined that it wasn't  worth limited benefit due to the much extra cost involved.

[bevans6]

Thinking about this, two strokes have two issues with oil.  One is ash, which is a byproduct of combustion of additives in oil, additives that are good and helpful in most engines.  Two strokes burn oil far more prodigiously than typical four strokes, and the ash affects the piston rings.  The other is heat, particularly at the rings, since two strokes don't have an exhaust stroke that cools the piston/ring package.  This is what defeats typical viscosity modifiers that give us multi-weight oil, and contributes to the ash issue.

Modern diesel oils have very low ash content, primarily due to the need to work with modern soot and pollution controls.  So they by and large meet that standard for two strokes.  However, they haven't been tested since the two stroke test has been obsolete for many years.  So you don't know if what they added to replace the old additives does any harm.  It probably doesn't.  Modern synthetic oils are vastly superior in terms of dealing with heat.  It's one reason they are used in about all racing engines everywhere.  So that is OK.  Modern synthetic oils have a naturally wide window of viscosity, and some 10W-30 synthetics might have about zero modifiers to gain that rating, they have it naturally.  Now, of course, they go so far as to offer 0W-40 oils, which I used to use in my Powerstroke diesel engine in my pickup truck.  But a synthetic 15W-40, Rotella has one, might be just fine to use in a two stroke.

Of course, at $50 a gallon, I ain't gonna use it.  I burn that off pretty quick...

[sledhead]

I use 5w40 synthetic diesel oil in my cat and other diesel engines I have

I buy it on sale for about $100 - $ 110 a 5 gallon pail

https://www.canadiantire.ca/en/pdp/motomaster-5w40-synthetic-diesel-engine-oil-18-9-l-0287944p.html#srp

but never used it in the 6v92ta

dave

[luvrbus]

Royal Purple was the only oil co that made a 40w synthetic  for Detroit's fwiw  oil consumption is to great on a 2 stroke for the cost of a synthetic stay with Mobile Delvac 1240,Delo 100 or other brands the Ammsoil is 15/40 they say is rated for a 2 stroke   

[Oonrahnjay]

I use 5w40 synthetic diesel oil in my cat ...
dave

      Same for my TDI VW.  I'm about to turn over 500K miles, still purring like a kitty.  But I don't have a 2-stroke diesel engine (in anything); the service guy at Onan says that the 5W-40 (Mobil Delvac diesel, packaged as "Light Diesel Truck" oil, sometimes when you can catch a sale about $24US at duh Waw-M*rk) is a fine oil for my generator. 

[Sebulba]

Unfortunately not all synthetics oils are what they are cracked up to be -- like anything else.

I have run Amsoil in every engine I have owned for 35 years.  It is amazing oil.  Back about 30 years ago though, big oil got it in their head to have a synthetic.  It was junk and really made a bad name for synthetics for a while.

Now, I know a 2 stroke Detroit is a different beast, so I am not sure how I would proceed were I to get one of these beauties, but I have nothing but good to say about a quality synyhetic.

My 2 cents

Seb