Ron S., when David Kirk rebuilt a K301 for me, he recommended straight 30W oil for break-in. Here's what he provided as a break-in procedure. Note this was for a modified high performance Kohler, aka
"Killer Kohler" so the RPMs listed are higher than typical for a plain rebuild.
<blockquote><hr size=0><!-quote-!><font size=1>
quote:</font>
1. Fill crankcase with Resolute brand, non-detergent, straight 30 weight oil (available at Fleet Farm). 1.5 quarts required.
2. Start engine and run at a fast idle (approximately 1500 rpm) no load for 30 minutes. Shut down and allow to cool for at least 1 hour.
3. Remove top air baffle, spacer nuts and spacers from studs. Retorque head bolts in proper sequence as given in the Kohler shop manual. Torque to 28-30 foot pounds. Reassemble baffle and remainder of components.
4. Start engine, warm up, and set governor high idle speed to 3900 rpm. Do not exceed 4000 rpm due to safety concerns with stock flywheel.
5. Run the engine as you normally would under loaded conditions, such as mowing. This will allow rings to seat faster. Don’t lug the engine – keep rpm’s above 3000 when under load as this provides the proper cooling air flow. Check the flywheel grass screen often and never allow contaminants to hinder air flow.
6. Change oil after approximately 2 hours of running while engine is still hot. Clean magnetic plug. Metal “whiskers” on plug are normal at this point in the break-in process. Refill with Resolute brand, non-detergent, straight 30 weight oil.
7. Change oil after approximately 3 hours of running while engine is still hot. Clean magnetic plug. Fewer metal particles on drain plug should be observed at this stage of break-in. Refill with any reputable brand of 30 weight automotive detergent mineral oil (no partial or full synthetics at this point). If operated in temperatures below 32 deg F., use 10W-30 multiviscosity oil.
8. Change oil at 20-25 hour intervals. After 40-50 hours have been accrued, engine is considered fully broken-in. At this time, full synthetic oil may be used and is recommended. Use 10W-30 Mobil 1 or Amsoil. Change interval may be increased to 40-50 hours using synthetic. A good rule-of-thumb…when oil starts to darken, change it.
9. Fuel – 89 octane (mid-grade) is a recommended gasoline for most operating conditions. 87 octane can be run in cooler weather. You may run 91 octane without any ill effects, but is a waste of money. It is highly recommended that Marvel Mystery Oil be always added to the fuel in the ratio of .4 fl oz (12 cc’s) per gallon. This ensures that combustion chamber deposits are held down and valve guides/stems are lubricated. There is no need to add MMO to the crankcase oil, especially when using synthetics.<!-/quote-!><hr size=0></blockquote>
