Mobile (sic) 1 20-50 synthetic

[John Larson]

That would be "Mobil" 1, NOT "Mobile" 1.  10w30 is too thin for the T44 
and T89 I5 engines, especially in temperate and hot climates.  20w50 is 
specified and works best. the earlier V6 engines need 5w30, 10w30, or 
10w40, depending on ambient temps and driving conditions.  Later cars 
like thinner oil (the use of thinner oils originated in a search for 
improved fuel mileage and the engines were redesigned to use them).  The 
owners manual for my 95A6 warns that 5w30 is inappropriate for sustained 
high speed driving.  Earlier engines such as ours were not designed for 
thinner oils, and 30w is just too thin for warm/hot weather driving.  John