I have been running 10W30 motor oil in my SUs for several years. I started with ATF, but it ran like a cold Ford. (The engine would lean out and almost stall on sudden acceleration). The 10W30 may be a bit heavy, but it is easy to get and seems to do the job.

The majority of posts that I had read before the refurbishment was a straight 20 weight oil. That was easily found on my shelf as "John Deere Hydrostat Oil", straight 20 weight no additives or detergents. It has worked fine in both sets of carbs that have been on this engine.

IIRC, each carb will hold about 2cc of oil. I use a 6cc medical syringe (w/o needle) to fill with no mess and correct amount.

Bonzi Lon

The majority of posts that I had read before the refurbishment was a straight 20 weight oil. That was easily found on my shelf as "John Deere Hydrostat Oil", straight 20 weight no additives or detergents. It has worked fine in both sets of carbs that have been on this engine.

Bonzi Lon

Another straight 20 weight, no additives or detergent oil is "3 In One" _Motor Oil_. Not the stuff in the white and black cans, er, bottles found in every home in America, but an oil for larger electric motors. Comes in a blue and white container.

Chris

ATF seems to work up in chilly Alberta, I've tried heavier oils and on cold days they seem unhappy about it. 10w30 seems to be my oil of choice for my 20-30 C ambient summer temps. ATF also seems to need to be topped up a lot more often.