Originally Posted By: CATERHAM
The main purpose behind the ultra high VI OEM 0W-20 oils such as TGMO (216 VI) is fuel economy. Compared to a typical 5W-20 (150 VI) it's a whopping 50% lighter at 32F, 35% at room temp' and still 10% at 90C (normal operating temp'). Both oils having the same 2.6cP HTHSV. It shouldn't come as a surprise that Toyota claims a fuel economy of at least 2% depending how the vehicle is operated.
If you mainly only do short-trips that's certainly useful. However, most don't.
At least 2% improvement.. depending on how the vehicle's driven. Well which is it..
Toyota 0W-20 has a tremendous amount of moly, how much of the fuel economy benefit is in that..
Where are you getting a 10% difference in visc at 90C from. If you use the Toyota VOA as reference with 8.54cst 100C and VI 210, that comes out to 38.44 at 40C. For the same 100C visc, VI 150 produces 49.64. That's 10.6 vs. 10.3 cst difference at 90C, or 2.9%!
Some of ACEA fuel economy specs call for a 3% improvement in a 30wt against a 15w40. Using the mid-points of 30wt and 40wt grades, that's 10.4 vs 14.4 cst. That's almost a 40% difference in kinematic viscosity for a 3% fuel economy gain. You expect us to believe a 3% difference in visc is supposed to produce a 2% fuel economy improvement, really?
Blindly recommending high VI without looking at the application is silly.
This is without even getting into your recommendations to people to mix oils different oils willy nilly.
A former Mobil1 Chief Engineer posted this in 2011 in another forum. Things here have gotten worse since then.
Quote:
The BITOG site has a lot of "experts" that say all sorts of things about oils. Until I joined here, I never looked at that site much because of what I would read the posters say or comment. All I can say is, that you should do your own research on oils, Mobil 1 included, and not rely on BITOG site for definitive conclusions about any one's engine oil and its capabilities.
