Straight SAE 40 VS. 15W40

worked for a bulk oil jobber. In the winter at about 10 degrees or less 15w 40 was harder to pump and slower pumping than straight 40 explain that.

 

You should have asked if anyone is using SAE40 compared to 15W40 and if they would give an oil sample reading you probably would not have had the negativity that you are getting. And I was curious as to why you would ask someone to do that experament instead doing it yourself kind of gave me the impression that you where afraid until I read that you where in the military. Thank you for your service.

 

Another thing that might be gaining you some grief is why would you mess with something that works. The newer engines have to have CJ-4 oil anyways, I don't think there is any straight weight oil that meets these requirements.

 

Two stroke Detroits fire twice as often as a four stroke engine and two stroke Detroits have a short stroke in comparison to other engines being used. This is why you can get it to fire up with 40 wt in 30* weather.

 

I am very lost here.

I have an 1988 MCI 102 C3 Bus with a 5 Speed Tranny and 8V92 Engine. I wanna put straight SAE 40 Oil in it.

I only drive the bus on 4-6 Trips a year and the bus will be running for 30 hours straight each way over a weekend (60-70 hours in a weekend, 4+ times per year). Half in Summer, Half in Cold Canadian Winter.

An MCI endorsed mechanic recommends highly I put in 15w40 and so does a good friend of mine. Everyone online says to do the 40 weight. I gotta make a decision on this by tonight.


PS. This is my first post! Thanks for your knowledge and experience!

 

Your engine requires an sae 40 oil. On a two stroke there are no advantages I know of going to 15w40 except cold starts. You could have problems with oil consumption and exhaust valves going with 15w40.



The one gentleman is mistaken about viscosity. Out of the bottpe a sae40 is always thciker than a 15w40 below engine operating temperature.

 

The engine design requires straight SAE 40w as recommended by the manufacturer, Always did and always will, that's the fact and no opinions will change that. Oil consumption increases in a two stroke Detroit when using 15-40 oil.