I got the sample through MBCA member George Murphy. the TBN did cost $6 extra. He said that fleet managers replace their oil when the TBN reaches 1/2 its original value. In the case of Mobil one that would be 11.3/2 or 5.6 since I have about 9k on this oil I'm losing TBN at a rate of 4.3/9k or about 0.5 TBN per 1K that would say I have about 3K more miles on the oil. That works out to 12K. Maybe the guys at Mercedes know what they are doing after all. Having said that George Murphy the MBCA tech guru recommends 6.5k oil changes. I spend my life doing engineering calculations and it is hard for me to go against the data and follow his recommendation, though the 2009 10k oil change posted above gives me pause.

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MBlovr
'59 180 Dad's original
'59 180 Dad's 2nd one
'67 250SE Dad's last one
'59 220 SE My first one
'62 220SE Coupe second one
'89 190E 2.6 5spd third one
'06 E350 4matic (sold)
'10 E350 4matic

MBlovr - What are your driving habits? That impacts the issue greatly.

I drive 110 highway miles a day and no short trips inbetween. FSS lets my Diesel go 15-16k miles before it trips. Its set for the 10k mile interval. I'm at 250k miles; sent my first oil test off last week just for giggles since I'd never done it before.

Someone only driving short city trips would expirience VERy different results using FSS.

Those driving 80's era vehicles and using dino oil should ignore all extended interval threads. Its not applicable to their engine.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

I think that this is a key issue. I am very light on the throttle and drive about 35% in town and 65% highway and get OBC mpg of 23 which is testament to my light throttle. I think that this helps me extend the oils life.

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MBlovr
'59 180 Dad's original
'59 180 Dad's 2nd one
'67 250SE Dad's last one
'59 220 SE My first one
'62 220SE Coupe second one
'89 190E 2.6 5spd third one
'06 E350 4matic (sold)
'10 E350 4matic

I have to butt in here a bit. Mercedes-Benz does not care about SAE, nor do they spec any oils based on any SAE specifications. Mercedes has oil specs based on their own test criteria, I believe the spec for most modern MB's is the 229.5. It will be specifically listed on the bottle of approved oils. The Lubrizol tool below shows some of the differences in different specifications in a neat chart to help visualize. Also a link to a list of MB approved oils for specification 229.5.

dataStack

MB 229.5 - Multigrade engine oils (Specification 229.5) - Mercedes-Benz Specifications for Operating Fluids



Let us also not forget that TBN depletion is not linear. Just because it may appear at first testing that it's 'using .5 TBN per 1k miles', it does not mean thats how it has trended since new. Perhaps it sheared 1 TBN or more per 1k miles early on, and tapered down as the oil settled in for the rest of it's useful life? Maybe it's the opposite, perhaps it's very low at first, and as it gets older, TBN depletion will ramp up to well over 1 TBN per 1k miles until the end of ti's useful life. You can't make these kind of blanket statements, as without data or consistent oil analysis over time, there's no way to really know.

This is a 6 year old thread…wth!

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....just drive'em!
'89 300TE White w/Blue, 152K SOLD!
'93 300E Blue w/Tan, 154K SOLD!
'01 E-320 4-Matic wagon, 130K
'67 Vette Conv. White w/Blue, 217,421K