From my S90 owner's manual (in boldface type):

"Extra oil additives must not be used unless advised by an authorized Volvo retailer".

Also in bold: "..15W40 should not be used under normal operating conditions."

Conclusion...Volvo do not want the thicker oils (or thickening additives) in this engine. For heavy duty use (like trailer towing in hot weather) the book recommends synthetic 10W30 oil in preference to a 15W40. Your engine holds nearly 6 US quarts and has an oil cooler. No need for heavier oils.

The owner's manual for my XC60 recommends 5W30. Its engine has many mechanical similarities to the S90, but has 100+ more HP, is turbocharged and is pulling a heavier vehicle. Still, the lighter oil is recommended. I use Mobil-1, 5W30.

And ATF may have some good detergency characteristics, but it is not designed to handle combustion temperatures. It is mainly a hydraulic oil.




--
Bob: Son's XC70, my 83 244DL, 89 745 (V8), 98 S90, and XC60. Also '77 MGB and some old motorcycles

Hi,

I can only comment the use of oil additives from my limited experience. I've used STP, Bardahl, Lubro-Moly, Marvel Mystery Oil and Morey in the past. Lucas no (not available here). Most are oil thickeners especially designed for older engines with increased internal clearances from wear. These quietens the engine quite a bit. For Lucas, it looks like it may be an oil thickener also, reading from their MSDS.

There are many schools of thought regarding what caused engine wear. Some attribute these due to oil leaving the combustion chambers when engine is stopped. For this line of thought having a thicker oil would lessen this effect - thus using oil thickener. Other school of thought thinks if oil can be made to travel faster to combustion chambers during start then this would lessen engine wear. They would advocate using the thinnest oil the engine can take - thus favours using lab-based synthetic oil with uniform molecules to reduce internal molecular resistance impeding oil flow.

For Volvo engine I don't think they benefit a lot, except maybe Marvel. I occasionally use them prior to oil change and noticed that when draining the used oil the internal parts (looking thru the oil filler hole) a tad cleaner.

Nowadays I think these additives are just a quick way to make money, same like selling bottled mineral water. And the topic of engine oil with additives or not have been discussed ad-nauseam in many forums. Lets start enjoying life instead!

Regards,
Amarin.

the .5 atf doesn't. I don't now what the lucas is for. atf is a better cleaner than oil is. seen a few shops that do that. good luck, chuk.