Best oil to use (Viscosity)

[pookiebear]

In a relatively high mileage car(200 000km ), what is the best oil viscosity to use in my 93 E320 . I do tow a lot and also get caught up in traffic from time to time.

I currently use a 15W 40 (Castrol GTX2), but am worried that this might not be the ideal. I do change oil every 10000km. Car doesnt not use oil between changes. If I change to a high spec 10w 60 would this be ok?

I also have an old 88 300TE with over 300 000km. I use a 20W 50 (Castrol GTX) as I found if using the 15W 40 oil, she used nearly 2 pints per 1000km, on the 20W 50 ,use is now one pint per 1000km. This vehicle was a one owner when I bought it (with complete service sheets/books), and he had complained from new that it used oil (When new one pint on 2500/3000km (Merc agent said within specs on job sheet). It is not the valve stems as all have been changed, and compression is still within specs over all 6 cylinders. I was told by a Merc mechanic that the older M103 engines had a design that they used oil through the control rings, is this true? I do remember a freinds dad back in the late 80's having an issue with oil consumption with his new 260E, and the Agents said it was with in spec...

 

[grober]

For your E320 a good semi-synthetic 10w40 ---- look for MB 229.1 Approval as minimum spec [ no Castrol products please !!!] Fuchs TITAN XTR 10w-40 [= MB factory fill,] Millers Oils XSS 10w-40 , Mobil Super 2000 X1 10w40, Shell Helix HX7 10W-40 , changed with filter every 6,000 miles would be my recommendations.
For the "oil burner" M103 the cheapest 20w50 that meets MB spec. If you are getting a lot of piston ring blowby you might find it an advantage to run a diesel engine oil of equivalent spec?