I bought a '96 Toyota Avalon a couple weeks ago for $2,800 with 184,800 miles. It had no maintenance record, no service history, nothing. The oil had been changed a month before I bought the car though, and the engine seems to pull strong - and it passed smog easily when I tested it. Still, I've been afraid of the 1MZ-FE engine being a big ole bloody sludge beast, and ordered 4 bottles of Auto-RX. I figured that I'll need all the cleaning I can get! In the meantime, I decided to open up the valve cover to replace the leaky valve cover gasket and get an idea of what I'm up against. The result was surprising. 185,000 miles on the sludger, remember! Oh wow. Buttoned her back up last night and took another picture for the heck of it. How can I tell if this is the original engine? Does the serial number of the engine need to match up with the VIN number?