I only noticed when i turned the main gear and the front and back wheel hubs turned in opposite directions!
Please post a detailed shot of the underside of the front axle, the servo arm and connection to the steering. The supplied steering servo of mine has a very crappy looking arm, and I'm not happy with the way it connects.
I think they work without, veg oil seems a similar consistency but I think the silicon nature of the proper stuff is good for lubrication etc. Its cheap off ebay though, I used 30wt