My understanding from Mobil has always been that their synthetic diesel oil (e.g. Mobil 1 Turbo Diesel Truck 5w40) is compatible with their mineral diesel oil (e.g. Delvac 1300 15w40). However, I must confess to being a little unnerved to discover that I have a head gasket leak immediately on the heels of my adding about a quart of dino to a system with synthetic in it. (In case you're wondering why I did this....I knew I had a leak somewhere and didn't want to add "liquid gold" until I diagnosed and fixed the leak.)

So is there even a chance that mixing the oils could have accelerated the head gasket failure?

FWIW, Mobil tech support says no, no chance.

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

No.Hot Rod Magazine in the 80s reccomended to save your money add one quart sync. to the rest dino,for the same protection when racing

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

Could be that the clean oil cleaned up whatever is it that was clogging the fault so you got the leak right then... Hard to tell though, but in a normal motor that doesn't happen. (I've mixed oils on my engine and it's running just fine)

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[/SIGPIC]~cirrusman

1983 Mercedes Benz 300SD - Wife calls him "Chitty Chitty Bang Bang"
[SIGPIC]




1983 Toyota Tercel (Tommy, The little Toyota that could)
1965 Ford F100 (Grandma Ford)
2005 Toyota Sienna (Elsa, Wife's ride)


Gone:
1988 Toyota Pickup
2004 Subaru Outback

1987 Cadillac Fleetwood Brougham
1986 Volvo 740 GL Station Wagon - Piece of junk.
1981 Volvo 242 DL 2 Door - Hated to see it go. R.I.P.
1987 Pontiac Fiero GT

The answer is in your question, but you just phrased it wrong.

Your mystery leak was the head gasket leak, adding more oil didn't change anything-you just got more sensitive to it.

Kind of like this one: "After putting a new muffler on my car, all of my interior panels became loose and rattley all at once." The panels were always loose and rattley, I just couldn't hear them over the muffler until I replaced it. Correlation vs causation.

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$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment

Part of the ambiguity was that I knew I at least had a leak at the stop lever o-ring. So I hoped that, by fixing that, I would stop the leak. Turns out that was the least of my problems.

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

I feel your pain. I keep telling myself that my gasser's idle knock is a loose bracket somewhere and not a sloppy valvetrain

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$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment

Sounds like your gasser is hinting you to get a diesel...

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[/SIGPIC]~cirrusman

1983 Mercedes Benz 300SD - Wife calls him "Chitty Chitty Bang Bang"
[SIGPIC]




1983 Toyota Tercel (Tommy, The little Toyota that could)
1965 Ford F100 (Grandma Ford)
2005 Toyota Sienna (Elsa, Wife's ride)


Gone:
1988 Toyota Pickup
2004 Subaru Outback

1987 Cadillac Fleetwood Brougham
1986 Volvo 740 GL Station Wagon - Piece of junk.
1981 Volvo 242 DL 2 Door - Hated to see it go. R.I.P.
1987 Pontiac Fiero GT

How do you know you have a head gasket leak?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

And what is leaking and exactly where on the head gasket?

Coolant to combustion chamber ( and combustion to coolant )

Coolant to external.

Coolant to oil ( and sometimes the other way round )

Oil to external ( usually only on engines that have pressurized oil running through the head gasket, sometimes return oil can leak from the head gasket , See M104 straight 6 )

Oil type won't cause any leaks, low viscosity can increase leaks but , if that happens, there was already a leak there.

All I really know thus far, from Mechanic #1, is that he's pretty confident that I have a head gasket leak of the type where oil is getting into cylinder #1. I am taking it to Mechanic #2 next week (he has much more regular experience in dealing with head gaskets) to confirm the diagnosis and, if confirmed, replace the gasket. Will set me back $1500, but I'm confident it will be done right.

Just for grins, I asked the dealer their price. $2400.

__________________
14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

$1500 just to replace a head-gasket...?

I'm in the Wrong Country!

Be expensive at $500 over here!

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http://i190.photobucket.com/albums/z...0TDnoplate.jpg

Alastair AKA H.C.II South Wales, U.K. based member

W123, 1985 300TD Wagon, 256K,
-Most recent M.B. purchase, Cost-a-plenty, Gulps BioDiesel extravagantly, and I love it like an old dog.

W114, 1975 280E Custard Yellow,
-Great above decks needs chassis welding--Really will do it this year....

How did he figure out oil was getting into #1?

The Welsh must be cheap.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

What makes them think that oil is getting into the cylinder from the head gasket? If that was the case, your oil pressure would be high and erratic as combustion gasses are entering the pressurized side oiling system. On various engines, at most I've had pressurized oil leak outside the gasket but not to any other location. These leaks occur because the through gasket oil port is usually near the edge.

There needs to be an actual diagnosis before changing parts.

What are the exact symptoms?

Fairly common problem if that is what it is. Certainly not type of oil used.

Try to get the most improved head gasket as efforts were made to reinforce this particular area of the replacement gaskets over time.

Actually I suspect it was an engineering error that unfortunately was left in production. The oil feed passage to the head is too close to the bore of the number one cylinder.

$1500 is not a bad price for retail here. I would ask whether they use new head bolts or reuse the old ones, do they spec a quality headgasket (there are 2 grades, OE or Victor Reinz are best) and will they have the head checked for flatness and possibly incloude a skim cut if necessary (some mechanics will do that out of habit 100% of the time, its about $325 for that at a machine shop and of course they will pressure check the head to assure it has no cracks, this is especially important with aluminum diesel heads but gassers also have problems due to coolant eating the head away from the inside if the antifreeze isn't replaced regularly and of the right type (MB spec).

Some mechanics will reuse the old headbolts and mic them according to the FSM first to see if they have stretched substantially. I always insist on using a new set at around $60 that is cheap insurance that you won't break a head bolt torqing the head back on and if you do then you have to pull all the bolts the head and remove the broken bolt and as you can expect it then gets really time consuming to rework so some places will include worst case things like this in an estimate.

Labor rates at shops run from $100 to $125 per hour in the northern Calif San Francisco Bay Area but the thing that some shops do is charge the full service time in the book (well nowdays on CD-ROM or online info base). Even if the actual job takes say 65% of the book time, they charge the full estimated time. This can stack up due to several jobs involved.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!