Piston Slap: Wither Synthetic Oils?

TTAC Commentator Halftruth writes: Sajeev, I am in the market for a new mid size truck. I have been looking at Tacomas both new and used and came across a used one at a decent price. Thing is, the owner states that "purchased new and immediately changed all fluids to synthetic from the oil to the rear diff". I am not crazy about this as I have heard of nightmares from folks going to redline, purple stuff etc etc for a better (shift, mpg whatever). Why dont folks leave well enough alone? What is your take on this??? Sajeev answers: Considering many vehicles run synthetic (motor) oil from the factory and even more run semi-synthetic stuff, I'm pretty much indifferent.  Making the switch in the first few years of ownership isn't gonna hurt anything, provided you use the right weight/type and there isn't a huge warning from the manufacturer about deviations from the factory stuff. (Subaru, Ferrari, BMW have all done this in the past, IIRC.) Hell I switched to synthetic (engine) oil in my Mark VIII when I bought it at the ripe old age of 117,000 miles!  Aside from one common gasket fail point, I had no problems. So why not switch to a full synthetic for most vehicles?  You gotta love your ride for the next 10-20 years, that's why not. That said, I switched my Ford Ranger over to Mobil 1 after 6,000 miles…so I guess I'm in it for the long run, too. Perhaps synthetic rear axle fluid is also better, but I've switched before and never noticed a difference.  But, on an older vehicle, if you're going in there for something else…might as well make the switch. Transmissions?  That's where the shit gets real.  The sheer number of fluid requirements for gearboxes (mostly automatics) is more than a little horrifying.  You gotta be REAL careful here. Any aftermarket synthetic oil you choose had better be compatible with the factory fluid. So do your homework: like a Q&A session with an answer right from the horse's mouth. Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you're in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice. from The Truth About Cars http://www.thetruthaboutcars.com

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