.. motor oil through the fuel tank? I have a couple of old bottle of castol 20-50 I never used on the 420. Neither of my cars uses that oil and I have no use for it, Especially since its been in the weather for a few years. I read you should never keep oil long periods of time in the garage. I was thinking of just tossing them in the fuel tank next fill up. Any problems I might encounter?

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual

Do it over a few tanks of fuel would be best. It will make your injectors quieter.

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Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

According to what the early Mercedes diesel operator manuals said, you could do that if it was non-detergent oil, such as straight 30W or 20W, because it was pure oil without any additives.

The 20W50 will have viscosityadditives.

However it is used in Citroens, so you can send it to me

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Strelnik
Invest in America: Buy a Congressman!

1950 170SD
1951 Citroen 11BN
1953 Citroen 11BNF limo
1953 220a project
1959 180D
1960 190D
1960 Borgward Isabella TS 2dr
1983 240D daily driver
1983 380SL
1990 350SDL daily driver alt
3 x Citroen DS21M, down from 5
3 x Citroen 2CV, down from 6

Dump it in. 2 quarts of clean motor oil even mixed into as little as 2-3 gallons of diesel/Kerosene/home heating oil will be fine having no measurable effect on your fuel system/motor.

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83 300TD (need rear wiper assembly dead or alive)
84 300SD Daily driver
85 300TD almost 400k miles and driven daily.
98 E300D *sold
86 300SDL *sold and made flawless 10 hour journey to new home.

already did. I didnt notice any difference good or bad.

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual

Funny, I was cleaning out a friends garage this evening and came across a few quarts of oil and atf that were older stock left over from vehicles or projects long gone. I just poured it into the tank. Mixed with 10-15 gallons of fuel, it doesnt amount to much.

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83 300TD (need rear wiper assembly dead or alive)
84 300SD Daily driver
85 300TD almost 400k miles and driven daily.
98 E300D *sold
86 300SDL *sold and made flawless 10 hour journey to new home.