I am doing the first oil change on my M103 ('88 300SEL) since I have owned it. I have put about 3200 miles on it since I bought it last October.

My car has around 157K miles and at this point, it dont leak or burn any oil, which is rare for a M103 from what I have read. Mine may have already had work done to it in the past however.

I am wanting to get some advice from M103 owners as to what weight/brand of oil would be best for this engine for hot weather. I went to the dealer the other day and bought a Mercedes oil filter, so thats been taken care of. I will look in the manual tomorrow to see how much oil it holds. I am thinking it said 6 or 7 quarts? I may be wrong... it may be more like 5 quarts. I will check it out.

I have not even looked at it, but I am hoping that the oil filter is easy to gain access to and that my standard filter removal will take it off easily.

Thanks for any advice.

The oil filter is accessible from above. It's located on the driver's side behind the air filter assembly. If I remember correctly, the drain plug is 14mm. Hope this helps.

These engines do not have roller cam followers as do modern engines. For that reason, your standard Premium engine oils do not have a zinc additive that is required for long cam and lifter life. The oils that still have this are oils such as Chevron Delo, Mobil Delvac and Shell Rotella T. These oils are primarily designed for diesel engines but work out quite well in the M103. I have used Chevron Delo and my 300E now has 320,000 miles and is still in top shape.

I agree with Larry, I use Chevron Delo 15-40 all year round, but we don't get temp extremes here in the pacific northwest.

Years ago I would switch to Valvoline 20-50 in the summer months, but don't do that now because the change in oil formulation. With high miles and really hot weather you could probably use Valvoline, but you would have to add a zinc supplement. I think GM EOS (engine oil supplement) an engine break in product will fit the bill and is probably available at GM dealers now ( it was taken off the market for a while I heard).

Be sure not to overfill either. I have now switched to sucking the old oil thru the dip stick like you would with a boat, much easier on the back.

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1994 E320 Cabriolet
1992 300CE (Sold)
1991 300SE (Sold)
1986 560SEL (Sold)

I second, or is it third, the idea of using one of the diesel rated oils. I bought a 1989 300SE in March and did the oil changes with Penzoil 10W-40 until the last one, when I switched to Chevron Delo 15W-40.

Since I owned it the car has used about 1 quart per 1,000 miles, though it doesn't smoke and the plugs are clean. Since switching to Delo the oil level has scarcely moved since I changed it, 1,500 miles ago.

Like Nipperiley, I've just started pumping the oil out through the dipstick tube. With the top mounted oil filter, it makes oil changes super easy, quick and clean. I pump the oil into clean gallon milk jugs and drop them off at my local Auto Zone.

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2000 Mercedes S500
1990 Mercedes 560SEL
1970 Triumph Spitfire

I do not recommend using one of the gadgets to remove the oil. The reason is that oil change time is the ideal time to get the car high enough to get under so that you can not only drain the oil, but also inspect thoroughly underneath for leaks, loose suspension components and numerous other things that need to be periodically looked at or otherwise inspected.

I have heard about using diesel grade oil before in a M103, but this is the first time that I have seen a reason. Zinc additive for the cams.

So what about the recommended plastic fantastic Mobil Uno?

I have used Pennzoil Dino/plastic blend in the past but next time around I may try a diesel blend.

I don't like those vacuum suckers either. Get a sump bolt with a magnet on it to hold the possible filings.

Mobil One comes in a diesel version with the zinc additive.

what i do is only use Castrol 10-40 in the winter and 20-50 in the summer and Fram filters, they are A-OK. 7 quarts in my 300TE and good to go. I have used nothing but Castrol and Fram for 25 years on/in BMW's, Audis, SAABS and Mercedes with no 'oil related engine breakdowns'. It's true...

heck, I even had a Peugeot 504D and used Castrol in it and it ran from 50K miles to 150K miles

i use castrol 20-50 in my car. thats what was used by the dealer until the early 90's on my car. should i be buying a zinc additive?

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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

I use Rotella Synthetic 5w40 diesel oil....it seems to run quite well on it.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Curious as well, been using the same brand and grade.

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'76 240D 311K
'92 300E 100.001K
'87 300E RIP

Okay here's the deal with the zinc additive and the M103 engine.

To begin with the zinc additive is much more necessary during the cam and lifter breakin period than it is in a high mileage engine. Added to that is the fact that the M103 has what is called a sliding mechanism, not as much load concentration as is found in a flat tappet Ford or Chevy V8.

The universal grade (diesel) oils have other redeeming qualities. One is added detergents that will keep a gas engine squeaky clean inside. The Total Base Number test commonly performed on oils comes back with a VERY high number for Chevron Delo and I expect also with the other commonly used universal grades (Rotella and Delvac.)

Now for the testimonies such as "I've used nothing but my precious brand X for 25 years and my engines have lasted forever." That's all very nice except those oils DID have zinc additive in them until just a few years ago. At some point just a few years ago, the engine oil producers saw a way to justify a little extra profit for themselves. They justified the elimination of the zinc additive with the fact that all modern auto engines have roller followers thus not requiring it any more. Did they TELL you that they were dropping it out of the oil? I don't know about you, but they never told me. They just said the heck with those old Farts that drive old cars.

Since they just quietly started leaving out this ingredient, only the last FEW years of that "25 years and my engines run forever" period has been without this ingredient that is life blood for older engines without roller cam followers.

If you drive a car with no roller cam followers, use an oil with the zinc additive included. Do NOT add zinc to the oil with the exception of the break in period after cam and follower change. The reason is that too much of it can cause a sludge problem. The oils that use zinc as part of the blend are carefully formulating the balance of zinc additive with the amount of detergents. Don't try to home brew and achieve this balance. You don't have the lab that your sacred favorite oil maker has.

Use German oil filters, i.e. OE spec.

They mount upside down, and the cheapo PepBoys filters will dump all over everything and the good ones won't.

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Kent Christensen
Albuquerque
'07 GL320CDI, '10 CL550. '01 Porsche Boxster
Two BMW motorcycles