Guys guys guys, you are doing this ALL wrong. All you need is a leaky truck to avoid rust! Preferably the power steering, yes; But the other oils work as well. The under carriage of mine has been coating itself from the leaking power steering as long as I've had it, not a bit of rust!
Unfortunately he is right...... If you have looked at the Morning thread, you will have seen I have been looking at the dirty side of my VW A LOT here lately..... the car has 303,*** miles on it currently. The engine does "sweat" a bit of horsepower (not too much, it really doesn't have a lot to spare ) and the IP has been leaking the last couple of months. The engine is offset to the passenger side of the car.... the entire passenger side of the car has very little rust. When replacing the control arm I only had one rusted fastener, and it was the swap bar link out next to the wheel..... everything else was nice and oily. But, look under the drivers side, there is a rust..... nothing on that side to leak for undercoating.......
Buddy of mine just did an auto to manual conversion for someone on a 98 Cummins...... NOT A SINGLE RUSTED FASTENER!!!! Truck had been completely "undercoated" by the Cummins......