1990 Chevy S-10 Gas gets into oil

Could be a leaky injector/s or the fuel pressure regulator

if your truck does a lot of short hops, like a mile 2 miles or so and not driven at least 10-15 miles that is how gas gets into your oil. You fix it by changing the oil and filter. then if all it is used for is small hops then it should be changed every 2 months or so. that means oil and filter.

In other words what he's trying to say is the engine is not fully in operating temperature with short distances driving stop/go type thing and the unburned gas tends to go thru the cylinders w/o being fully ignited which can contribute to wear and tear on the lower end of the engine and burn out the catalytic converter-