Originally Posted By: Gebo
I was wondering if some of the additives in the European formula had some type of detrimental effect on egr, catalytic converters, and the various pollution stuff we have on our US domiciled cars.
Good point, IF you have an oil consuming engine, like consumes more oil than about ~1 quart in 3,000 miles or so, THEN the euro-spec oils like M1/Castrol 0w-40 for example, do have higher levels of phosphorous which can foul catalytic convertors. If your car doesn't consume much oil at all, its not a problem. Still, the euro oils don't really have that much more ZDDP phosphorous than the SN limit of 800 ppm in lighter oils, so its probably not a big issue at all.
No other detrimental effects, in fact mostly good effects! Just the mentioned 1 or 2 percent loss in horsepower and fuel economy, both. And the extra small amount of heat generated thru greater viscosity, again not too bad at all.