Originally Posted By: Capa
From what I am seeing from several sources on the Internet, in the US we drive our vehicles more miles than Europe or Australia. There is apparently no effect from Europe using thicker oils and the US thinner oils when it ones to longevity. In fact, given the data, ironically one could argue the opposite.
The vehicles in the US are lasting longer as we move from decade to decade and from thicker oils to thinner oils. I don't understand the complaint over CAFE when in the US we are reaping the benefits of better MPG and our vehicles are lasting longer!?!
Umm! The results of using light oil in engines where the design team originally specified that a 30 or 40 grade should be used are not likely to be known for some years by most owners, but the high approved oil consumption figures that are used to deny warranty claims make it obvious that manufacturers know the truth of long term light oil use.
Every engine is different in the way it responds to different oil grades and the useage or driver style also make a difference. Most of the light oil UOA data relates to VW engines as they reduced their spec from 40 to 30 some years ago and the VW TDI forum in Germany averaged out their UOA results to show that it was bad news, but the odd thing was that the cars that it was bad news for, were the ones owned by boy racers or high speed autobahn users who would have had higher cylinder head temperatures. Looking at individual UOA results proves nothing as the effects depend on the age of the engine, useage and driver style.
I am in contact every month with some of the ZF oil analysis geeks when I visit their R&D section and they are adamant that what is going on with oil specs as a result of CAFE is nuts, BUT the engines that suffer are most likely to be the non hybrid older block designs that are driven hard and are using cheaper 5/20's that shear to an even lower grade. It is most likely that combination that will suffer premature wear and the high oil consumption reports are confirming that even within the warranty period.
When you select an oil grade do remember that a cheap part synthetic 5w30 could well shear down to the same viscosity as a G4 full synthetic 0/20 by the end of the OCI, so if you want to move up a grade that has to be considered as you might need to stay with a full synthetic if you want to use a long OCI. The decision point for many engines in life expectancy terms is probably the oil consumption curve, if it starts to increase that is the time to think about moving to a 30 or even 40 grade.
Unfortunately the oil companies have to follow manufacturers recommendations, so the US versions of major brand oil finder pages are adding to the confusion, but if you check the UK or German oil finder web sites for the exact engine type you will see the truth and as a strong hint Liqui Moly have put a very specific label on their vehicle list for cars in the US. The Germans are world leaders in high tech oil development and when their geeks say something is a bad idea they are worth listening too.
I had to laugh recently because one fuel economy fan who was using 0/20 in a car that definitely needs 0 or 5w40 (It rattles when hot) said the car ran better after adding a can of snake oil thickner (It was an 80 grade oil plus some extra Zinc and Moly). He failed to understand that his hot rattle and oil consumption reduction was because he was in effect using a 40 grade oil.
