Originally Posted By: Skyship
The quality of the bearings in use in a modern 2012 spec car is often lower than those in a 2008 car due to back speccing that is rampant at present to reduce production costs. Some R&D effort was put into improving ring design to reduce oil consumption, but not bearings which is where the savings are being made. I suspect the article is even more valid in terms of main bearing wear than when it was written.
Advancements in bearing construction has come a long way in the last 10 years.
http://www.aa1car.com/library/ar797.htm
This thick/thin oil nonsense is just that nonsense.
Not every engine can run on 20w oil without sustaining damage but most engines can run thicker oil without damage thats true enough but..
With a very rigid bottom end, wider main bearing saddles and wider rod bearings together with a forged crank polished to work properly with xw 20w oils and the correct bearing materials there is zero issues running it.
Just putting a high flow oil pump with a larger sump is not the answer as it wont eliminate crank or block flexing which because of the tighter clearances could allow the crank to break the oil film and contact the bearings.
When i read this rubbish about going thinner because its better i really get annoyed as it shows a lack of understanding of what the engine needs to actually use a thin oil and be reliable.
Thinner is seldom better in engines that spec xw30 or xw40.
Many older diesels can in fact use thinner oils than original spec because their bottom ends are massive built.
An engine with a cast crank thin saddles using bimetal/trimetal bearings with a non reinforced block and 2 bolt mains is not a candidate for 20w oil no matter how large the sump.
If xW20w is in the owners manual as a year round viscosity the engine can use it without damage or excess wear and tear in most situations in the country the car was sold in.
Whether its optimal or not in all conditions is open to debate but thats another story.
IMHO back specing is mugs game, a hail Mary pass if you will by the manufacturers to cash in on CAFE credits.
Take the older Ford modulars they back spec the thing to 20w but have a proviso that GVW cant go over xxxx pounds.
Thats a sure indicator that something in that engine is not up to snuff that has been corrected in later variants.
Personally i wouldn't put xw20 anywhere near that engine for year round use.
IMHO the thinner oils are a CAFE driven thing but that doesn't mean the engine cant be modified to use it.
Take unleaded fuel, in the beginning there were lots of problems with valves but technology and better metallurgy took care of that issue, now no one even thinks about no lead fuel.
I have nothing against 20w, 30w, 40w oil they all have their place what i do have a problem with is some posters giving the advice to use thinner oils in engines that were not spec for it because it can damage the engine.
The same cannot be said for using a 30w in a 20w engine, where no damage will occur.
Just a morning rant and my 2c nothing more.
