Is this ok?

[RBM 12]

Hello...I want to put shell rotella t6 5w-40 in my kohler k301? I just have seen people do this before...Will this better the engines lubrication system? Is it good insurance? What are your thoughts? Thank You.

[Darb1964 1,168]

I have used 15w-40 in some of my kohler in the summer and they seemed to do fine with it.

[953 nut 65,197]

Your engine is splash lubricated with relatively wide clearances when compared to a modern automotive pressure lubricated engine, I would go with 30 as stated in the engine manual.

 

[clueless 3,386]

 T-6 is not going to do anything better for you engine than T-1 (30w) or T-2 (40w). Full Syn and Blends in these old loose tolerance dirty port engines just burn off some of it after a couple of hours of use. Rotella T-6 is expensive overkill for these old flatheads.

[oldlineman 1,672]

I have used Rotella T1 30w for years, summer and winter without any problems. IMHO it is the best oil for these older engines that is made. Bob

[8ntruck 8,758]

  I believe that the Rotella T1 was originally developed for use in diesel engines.  It has a better extreme pressure additive package suitable for the higher bearing loads in compression ignition engines.

 

When used in our antique Kohlers, and Onans, that same extreme pressure package helps protect our journal type crank and rod bearings and the non roller lifters and cam shaft.  These surfaces have largely sliding type of friction.

 

The current automotive engine oils are designed for tighter crank and rod bearings clearances - often with special coatings - and roller lifters running on the cam.  All of these features are efforts to reduce friction and increase fuel efficiency, which, was not a concern when our antiques were designed and built.

[JoeM 9,762]

I use 5w-40 diesel oil in just about everything, one real advantage is the synthetic oils ability to transfer heat. And of course we are talking about air cooled engines.  

That oil is top of the line and will out preform just about anything out there. Most thoughts are built on old school thinking and not science. Part of my old job was closely tied to lubrication and we had a lot of sensors gathering data around the clock. Synthetic oils lowered internal temps up to 20%, at the first oil change. 

You have to remember those old service manuals were written over 30 years ago. Oil has come a long way since then, and if you want to use it, It will be fine. 

[rick 288]

Does the Rotella T-1 have more zinc additive than normal 30wt oil?

[oldlineman 1,672]

I believe so

[RBM 12]

I have about 4qts of this oil...Is it fine to use will it damage anything or is it just unnecessary? Thank you.

[ri702bill 11,825]

4 hours ago, 8ntruck said:

The current automotive engine oils are designed for tighter crank and rod bearings clearances - often with special coatings - and roller lifters running on the cam.  All of these features are efforts to reduce friction and increase fuel efficiency, which, was not a concern when our antiques were designed and built.

 

And their severe duty flat tappet ZDDP Zinc is 5% of what it was - due to the Zinc clogging catalytic converters. That is why modern car engines use roller lifters - no more flat tappets.

Rotella still has a reasonable amount of zinc in it. Not recommended - using just modern multiweight motor oil alone. You CAN use it with a rather expensive zinc supplement added to it. Better off just to buy the conventional (not full synthetic) Rotella. TSC - $16 a gallon.....

[JoeM 9,762]

17 hours ago, rick said:

Does the Rotella T-1 have more zinc additive than normal 30wt oil?

T-1 has about 1000 ppm zinc

T-6 is >1100 ppm zinc

Modern motor oils, for gas engines, used today have around 700 ppm

Racing oils 1600

Break in oils >2000

 

Don't get caught up in the more is better thing. Zinc alone is destructive additive and should be used in conjunction with other chemicals to form the proper blend.

Personally, I would never add anything to my oils. I would, like you are doing, get a good fit. 

If you really want to insure you have the best oil, Kohler sells motor oil that is to their spec with all the right additives and blends.

 

 

 

[rick 288]

I've been using Schaeffer's 7000 30wt. in my iron Kohler engines.

[Retired Wrencher 6,576]

I use a when I change the oil. It helps the tappets. 

[clueless 3,386]

On 4/21/2026 at 1:35 PM, RBM said:

I have about 4qts of this oil...Is it fine to use will it damage anything or is it just unnecessary? Thank you.

If you got it use it, it's still good lubricant just expensive and over kill for your engine, I would still change it at  25 hours, then just use T-1 or T-2.

Edited 3 hours ago by clueless

[peter lena 9,847]

@Retired Wrencher been using that  rislone zinc for  for years , 4 oz per 2 qts  of oil , bottle specs , often refer to it  for smoking engines ?  its VARNISH CUTTING ABILITY  IS AMAZING , would pick up a used  neglected engine , smoking , rough , run it in on a seperate gallon of heavily treated fresh fuel ? cleaned fuel bowl , STA BIL IN THE GAS . START  THE IMEDIATE REVERSAL  OF FUEL HOSE BREAK DOWN .while slowly recovering  engine function . detail in carb , and related linkage function , usually a  rusted / neglected mess . choke and related throttle,  plate barely  move , its amazing to me how close  , original  set ups were , verifying  insuring  areas , make them work with ease . just started up my  , 1982 ,c 85  , swapped in a 12 magnum years back , still my favorite unit , also my test bed for a lot of  ideas , pete