Straight SAE 40 VS. 15W40

I read an interesting post regarding the use of straight SAE 40 vs 15W40 in 4 stroke engines. Apparently, the use of straight 40 provides better lubrication and wear protection.

The only down side would probably be the thickness in the winter time. How ever, in 2 stroke Detroits, such as at the 8v71(aka 318 Detroit) and 6V92T they specify SAE 40. Has anyone here ever experimented with straight 40 in their 4 stroke Series 60, N14 or 3406?

If someone could do this and send in an oil analysis to see how your engine wears compared to a 15W40, that would make an interesting comparison. From what I can gather, both oils are 40 weight at operating temperature.

Since it is summer, if someone has done a past oil analysis with 15W40, would you consider running SAE 40 for one oil change and sharing your findings with the forum? Thanks!

http://www.busconversions.com/bbs/index.php?topic=13458.5;wap2

 

Thanks for the info, while 15W40 may be the ticket I'm still very curious to see results on paper. I would just be curious to see how fuel economy and wear patterns change. If there is one volunteer out there, that would be awesome. By the way, at a local oil distributor I picked up a 5 gallon pail of Rubia S SAE 40 for $45.00. The only negatives I could see would be increased wear to an engine. I enjoy learning new things, reading others opinions and studying fact. I know you're not arguing and I'm not trying to argue with anyone either, but just stating what my purpose of this post was.

If you know the location of any literature showing wear comparisons in a 4 stroke engine using 15W40 and SAE 40, I would like to see. Thanks.

If you look at the link below, there are pictures show the wear differences to various engine parts on a 2 stroke Detroit. I could NOT find anything showing testing in a 4 stroke engine, which is why I was asking if anyone wanted to volunteer. Testing used 15W40 in one engine and SAE 40 in another. http://www.tejascoach.com/ddcoil.html

 

If you're curious as to why I don't do it myself, one I don't drive commercially, I'm currently in the military. I have an 8V71N, 6V92T and a 11.1 Series 60 in three different private vehicles. I do not drive them regularly to get an accurate analysis. I just sent in my first oil analysis on the 8V71N that I just picked up with 15W40, just changed it to SAE 40. The only reason I'm asking is after reading a thread, which I posted where someone claimed to use SAE 40 with superior results. They provided no oil analysis, just went on the longevity of the engine. The 6V92T I have not done an oil change in 5 years, it's due for one but there is probably less than 1,000 miles on the oil with lots of idle time. The 11.1 Detroit I've only had for about 4 months, the oil was new when I got it.

As stated, I'm looking for a comparison. I have nothing to compare to at this point. I'm sure people have done oil analysis on their trucks with higher miles on the oil that could swap to SAE 40 for curiosity to see what results they would get.

 

Let's not be too over dramatic here. You're using a straight weight oil, not dish soap in your engine. I've done more than enough to lay out the facts. Do you seriously think your engine will self destruct on SAE 40? I'm not twisting anyone's arm into using SAE 40. Asking if anyone has factual information via oil analysis or is willing to try SAE 40 to get said factual information does not seem unreasonable. I've never said SAE 40 is a better oil for a 4 stroke engine. I'm simply trying to find scientific evidence to prove if it is or isn't. 15W40 is commonly used in a two stroke engine, in fact that's what the military uses in theirs.

Who's going to pay to contribute to a road service call when my Super Single blows out, since I can't limp it to a truck stop?