Lard-looking stuff is probably a mixture of water and oil. Condensation is natural in internal combustion engines and normally evaporates when the engine gets up to temperature. Short rides don't allow enough time or temperature for the water to be expelled and it mixes with your oil. If you pull your oil dipstick, you'll likely see water droplets on the bottom of the dipstick cap. Longer harder rides gets everything circulating and mixing, so the mixture got into your intake through the head breather system. Usually not a problem, but if your oil starts to look like cream & coffee, change it.
