Funny thing . . . I wouldn't recommend this though. I had an '87 Honda CRX Si that was an 'extra' car of mine. Had some damage & I used the settlement as a down payment on a new car. I was living in So Cal at the time. Relocated to Seattle, and didn't want to haul 3 cars up there, so I left the Honda at a friends warehouse.
For 3 and a half years, this car sat outside in Los Angeles. Through smog and heat and everything else including salt air. Since the car was in the corner of his fenced-in parking lot, he never had to move it or anything. In other words, I drove it to his warehouse, I turned it off, I pulled the parking brake, and I walked away.
Three and a half years later, My mother-in-law is in need of a ride. I have my father in law drive over to the warehouse and load this thing on to a half-trailer from UHaul. He gets two used tires installed on the rear of the car for the trip up to Seattle (the tires were rotting away).
The car hasn't been started at this point: I have the keys with me. He gets to Seattle and we push this car off the carrier. Man, I have never seen such a dirty car! I hook up some jumper cables and I swear that the car started up within 5 minutes of trying. As I remember it I had always used Castrol GTX 20W-50 in the engine.
On the odd chance that we could get the battery to hold a charge, we drove it around for a couple of miles. I saw a pressure wash place and pulled in. We left it running, and I must say it was running pretty smooth. I had the radio playing and the air conditioning on. At any rate, I ran to the 7-11 next door and bought a scrubber sponge and a can of Ajax. Completely scrubbed the car down from head to toe with Ajax. That's how much grime was on it.
When all was said and done, the car was clean, but completely covered in fine scratches. After a couple of applications of polish, a semblance of a finish reemerged on this car.
After this 'resurrection' I ended up driving the car for several hundred miles before changing the oil for the first time. The car was driven round-trip to LA at least twice, and when I was relocated to San Francisco I brought it with me. I used it as a commuter car for the two years we were there. If I had to guess, I put about 25000 miles on the car before it died. Timing belt broke, and it would have needed a valve job. I donated it to charity.
Here's exactly what I did to this car after my FIL drove it up to Seattle to the time it died for good: New battery, another two used tires for the front, and I changed the oil exactly 3 times. I definitely got my money out of that car.
All this to say: Maybe I should have used a clay bar on that grime!