Jewell Amber Oil genuine rocker box grease in cartridges which fit all standard "large" grease guns. Click product for quantity discounts. Remember to get a few of the 11oz "tubes" as well, since the (Alemite, zerk) grease fittings on the heads do not serve the valve guides, nor most rocker arm rollers, valve tips or pushrods.
If using in a conventional grease gun, this stuff can prove messy: Be sure to relieve the tension from the plunger below the grease when not in use, and store grease gun with plunger end upward.
For bulk users (regular flyers), quantity discounts available: see below item listing. Also, we now carry a small non-leaky oil gun to carry onboard the airplane.