A few years ago there was some discussion about what kind of oil to use in older engines. I'd like to see that discussion again to see what the final recommendations were dealing with the API Services, SL vs. SM. At the present, I use NAPA Fleet 15W-40SL in my 1911 T. I want to think that some component in the oil was left out when they added the SM label to the oil.
"A few years ago there was some discussion about what kind of oil to use in older engines."
LOL this is the understatement of the month. This year alone I've seen this thread pop up a few times. Just use the search feature on the board or search whatever you are looking for in google and add "mtfca" and you will find literally dozens of threads on oil - detergent, non-detergent, myriads of weights, the it-doesn't-matter-anything-now-is-better-than-85-to-100-years-ago-crowd, the folks that like additives, the folks that don't, and anything and everything in-between.
I was wondering what kind of oil to use in my doctor's coupe when I install a 24 volt distributor to make it start easier. Maybe these folks can help me.
You will NEVER get any kind of consensus from this crowd on "what oil is best" !!!! ;o)
That being said:
I subscribe to the "anything is better than 100 year old oil chemistry" so I use Walmart brand (which has all the API ratings anyone else has.)
I also subscribe to the "no oil filter, change it often theory", another reason to buy the walmart oil ... its relatively cheap.
I subscribe to the "less viscous oil gets to the bearings faster" theory so I use 5W-30 Walmart oil. (Added benefit .... free neutral! - my T has stopped trying to run over me if I forget to set the brake.)
and finally .... since the T does not have the high camlobe loadings that the older SE and motorcycle oils were designed to help, I don't worry to much about the API ratings.
Just one guy's logic .... bet you can find some disagreement !
Back in December of 2010, just prior to the completion of my engine rebuild, I posed the question as to what was the best oil and antifreeze to use in my engine and after a very long thread, including many of our most knowledgeable members, the consensus was to use the following:
Winter (or year round): 5w30 detergent
Summer: 10w30 detergent
I purchased the oil from NAPA.
50/50 mixture of IAT (Inorganic Acid Technology)
I purchased "Peak Zerex IAT"