Why I use straight wt oil

I have a old A/C crawler tractor I use for discing. Years ago I put shell rotola 15-40 in the motor. Shortly after that I experienced loss of power. Afer checking I found the cylinder walls were scored real bad. Ever since that experience I have used straight 40 wt with no problems./ I am finding straight 40 wt is hard to find in my area I found 40 wt oil for diesel engines. Would that be ok in my 60 year old gas engine? Stan

If you've never run detergent oil in an old motor it will break loose all kinds of crud from all over the first time it has detergent oil in it.

Straight weight oil can be hd or simply junk.. depends on how its made and what if any additives are in it. If you ran junk oil and then ran a modern oil,, it is possible that is started cleaning years of gunk off and cause trouble. Its more likely you switched oils because the engine was already on its last leg. The hd oil just happened to be in it.

That being said,, there are great hd 40 wt oils that have the exact same additive package as the 15w40 hd oils do. So changing in that case would do nothing but perform better in cold conditions and while warming up. Both oils would then act like 40 wt oil at running temperature.

Cheap or basic 40 wt with no additives will have lots of parrafin and wax products and will solidify and gunk up an engine. Pistons will score, or piston coaking. Rings will stick and, wear will be high. As the parrafin solidfies the higher end of the oil will vaporize out the breather and the oil will get thicker and thicker as your run it. Cam wear, tappet wear, scoring are all symptom of non detergent basic single weight oil. Sulfur will combine with moisture and become sulfuric acid and futher eat away surfaces. Non detergent oils performed based on the crude and some crude was full of wax, and sulfur compounds others were from light crude and generated a very "clean" oil. In days of old, the area and well the crude came from was extremly important as to how good a basic oil performed.

Today an hd oil is refined so that most all of the bad stuff is gone, and then a super additive package is added to fight acids, stop wear, stop sluge, stop coaking, stop vaporizing of the lighter componants, so that the oil is perfect for extended change intervals. Wear particles are kept from clumping together, keeping them at microsopic size so they they cant wear the engine, and so that they cant deposit on the engine as sludge.

Non detergent oil of any kind should only be run in engines with babbit bearings as modern oils will actually remove the soft babbit coatings over time.

Lots of the toyota folks are using hd diesel oils now to slowly remove the sludge from the probamatic engines. One of the problems is that every month, they have to drop the pan and clean the screens on the oil pumps as the oil slowy removes years of gunk. After about 6 cleaning the screens will not clog and the engines will slowly deposit the bigger stuff into the oil filters.

Urban legend

I think you are mistaken about the Babbitt bearing material. It is/has been my understanding that Babbitt is the material that MOST engine bearings are made from in modern engines. Bearings that I have worked with have a strong base metal coated with a copper alloy, and then coated with a gray metal that I have always been led to believe is Babbitt. Have I missed something over the years???

On the ACMOC forum it has been stated many times that multigrade oil in old engines is detrimental as their are additives that attack the old metal.
Diesel grade oil also has many additives to help cleaning the diesel contaminants
The old gas pony motors are recommended to use non detergent single grade oil which i use in mine.

My dad bought a 1978 deutz and used strait 30w non detergent until last year at that time (1978)deutz used it for break in oil..he thought that was ok to run it..i changed it over to 15w40 rottela last year,i filled with 30w non detergent oil and added 2 pints of seafoam..ran it for 2 hrs @ about 600 rpm and drained oil...it was black..so before I put the shell oil in I dropped the pan and it was very clean..and so was the pump pick up screen..i then put 8 qt rottela and 2 qt lucas oil and installed a manual oil pressure gauge and changed oil again..oil pressure has increased by 10-12 psi..i plan on oil changes ever 50 hrs for a couple more years..pull valve covers every other change to make sure they are clean...I had my doubts about this even working but it seems to be ok for now..keeping my fingers crossed I will never really know if the seafoam really cleaned the engine up or maybe it was clean already...who knows for sure.

Keith

Running strait 40W diesel oil is going to be the best thing for it. ALL the oil you buy now is for new engines and the specks on the crawler engine new are twice as much is a new one now, + 60 years of ware means you need thicker oil. It would not bother me to us it and maybe a bottle of STP per gallon of oil in it. You know as well as I do that 30 years ago strait 30W was thick not like it is now, Now its like 10W-40 use to be. I would bet that if you have a book for the crawler it says to run strait 30W when it was new. New engines have very tight tolerances and don't need that thick old oil instead them use 5W-20 that's thin. I don't want to get anything started so I will leave it at that. Bandit

I've used 15W-40 diesel grade Kendall oil in every engine I own,large,small,old, new for the last 20 years and never had a problem result from it.

No problem, Diesel is made to higher requirements than "Gas=rated" oils..

Ron.

I think you had another issue and are blaming the oil, thousands of people run that oil with no problems.

Multi weight oil even if it is SF-2 low ash will score sleeves and pistons on a two stroke Detroit Diesel.

If that was a 2 stroke diesel I stand corrected, here is an old post

http://www.yesterdaystractors.com/cgi-bin/viewit.cgi?bd=ttalk&th=1485858

Your link points back here.

Stan, I seriously doubt a few hours of 15w-40 were to blame for your cylinder scoring. But it wouldn't take much sand in the intake to do that kind of damage. At any rate, where you live it seldom gets so cold where SAE 40 weight oil would pose a problem, and any oil you buy today is going to be better than what was available when your Allis was built.

No sir. I was as surprised as you to learn of that a few years ago. I do recall as a youngster the term Babbit applied to Chevy blue flames before they were painted blue. Seems there was some sort of problem but nobody was smart enough back then or I wasn't around them to learn as to what caused the remarks.

Mark

Now seriously think about the evolution of oils... Back when your old crawler was made there were no additive ladened oils, just straight weights. The world has been sold a bill of goods to sell light end oils. When you shut an old engine down, you just need some residual coating on the parts, so that when you start up cold there will be some protection.

Newer high speed engines need different oils, but not the old engines. Heck the old tractor engines were broken in on Base Oils and run on them for years. Someone mentioned Kendall oil
as if it was an old stable oil. It is simply a brand name , made from various spot market base stocks, just like all the others.
My old AC M crawler runs well on about any oil.