Originally Posted By: 2015_PSD
I am new to the European car world, but it is fairly easy to see that 'thin oils' tend to be driven by CAFE requirements in the US--especially since Europe typically continues to use xW-40 oils as the OEM specification in most of their engines. With that said, my GLC specifies xW-40 and my wife's C300 specifies either xW-30 or xW-40 as the oil of choice. But based upon the viscosity results of the first UOA in my GLC, I am betting the dealer filled it with xW-30 despite the statement "Use only SAE 0W-40 or SAE 5W-40 engine oils
for Mercedes-AMG vehicles." in the owner's manual.
Time will tell if it was a mistake or shearing, but for me it is an easy choice (particularly with the clearance of Pennzoil Euro 0W-40 at Walmart these past few months)--I will be using xW-40 in all of my MB vehicles, because I see nothing to gain by using xW-30 in the C300 versus xW-40. I need to dig around and find the European owner's manual for the C300 (if they make that model in Europe) and see what is listed there for the oil.
Does Europe have CO2 and emissions regulations? CO2 and fuel economy go hand in hand.
Even Germany has fairly little Autobahn that can go long durations at speed. Even in the East, where there are longer more barren stretches, there are tons of Polish and Romanian carivans with 60-80kph limitation stickers, and most every interchange has a rapid deceleration to 80-120kph.
IMO, the heavier oil requirement is more for transient high acceleration compared to at speed cruising. Even if the power-speed relationship is cubic, it's not a huge amount of power to cruise at 120-160kph. Accelerating quickly out of the speed zones takes a lot more.
And AMG cars are the ones likely to be run at highest speed (so highest power, again the speed-power relationship) for as long as possible, with the same frontal area and relatively similar cooling capability. It makes sense to spec those cars (which are also more likely to be tracked or used on speed runs) than the others.
Europe is a cooler climate overall than the USA, and the speed limits in most countries are rather conservative, IME.