Will be picking up my 89 300e from my mechanic in a few hours. I finally went ahead and had new valve guides and seals installed. It'll be nice to have a dry engine again. You may want to sell your Valvoline stock now as I expect my oil purchasing will decrease substantially.

Here's my questions:

1. Should I go ahead and change my oil within ??? miles after the valve job, to prevent particulate matter from chewing things up?

2. To control oil consumption I've been running 20w50 dino oil all year round (probably OK anyway....Atlanta winter weather is still pretty mild). Now that my engine is sealed tightly (I hope) is this a good time to switch to synthetic? Should I consider a lower viscosity oil for the cooler months?

3. Should I expect any difference in performance after the valve job? If so, why? I wouldn't think it would make any difference.

Thanks for your sage advice,

to my way of thinking 20w50 is fine. How many miles on the engine?? If higher mileage - switching to synthetic may cause some oil leaks you never had before. My 2 cents worth.

I gotta back Moe on this one. On high mileage engines, switching to synthetic could be a bad thing -- you will probably spring an oil leak somewhere where you didn't have it before. The M103's are good for 300k+ miles easily, no matter what type of oil you run in it -- as long as you change it regularly.

How many miles on the engine?

~Paul

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'91 300E, 207k miles (20w 50 Pennzoil)

I recently switched to Mobile Synthetic with no proplems as far as increased oil leaks, (at 100,000) but I dont know how many miles is on yours. The reason it does this is because it can make seals shrink but if the climate is fairly mild then this may not be as much of a problem. For the added protection it would probably be worth it. My 2 cents

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88 300E
03 911 C4S
2008 Triumph Speed Triple

My pics --> www.BrettAdamsDesign.com

Some time ago, synthetics would cause leaks because they would clean the insides of seals and gaskets. Most, if not all, synthetics today have seal swelling additive. Therefore, older engines which didn't receive close attention to oil change intervals often have a varnish/crud material on the interior of the gaskets and seals of engines, transmissions and etc. If one then changes to synthetics, the detergent action will clean the varnish/crud off the seals and two situations can occur; 1. after minor leaking, the swelling additive in the synthetic will reseal a good gasket and you're good. 2. After leaking, the synthetic oil will continue to leak thru damaged seals and gaskets and you have a problem. It's your call on this! LOL, Roger

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Roger
1983 300CD 246k sold
1998 C230 52k
1980 450SL 75k needs AC
1999 Subaru Outback Ltd 43k

Sorry I left that out. . .the car has 125,000 miles on it.

I asked my mechanic about this and he said that if I was ever going to switch to synthetic, this would be the time as the engine is as tightly sealed as it will ever be.

Oil and filter changes were done routinely so hopefully there's not alot of sludge built up. I was warned about the potential leak problems before putting synthetic in my 911 but did it any way. Not a drop.

I think I'll drive about 500 miles (on the new oil & filter put in post valve job) then switch over to Mobil 1. I believe alot of the concern about synthetics is based on problems that occured in the early days. Modern synthetics are supposedly less prone to causing leakage. I sometimes wonder if my valve guides would have held up better if I'd been using synthetic all along.

Thanks,

Considering the summer temperatures in Atlanta, I would go to synthetic just for it's stability at high temperatures. My synthetic oil experiences:

1. A two year-old 1991 Dodge Monaco with a 3 liter V-6 (essentially a Volvo 164 engine) and 20,000 miles = oil leaks

2. Currently, a 1999 Ford Expedition with 41,000 miles = dry as a bone

Both vehicles ran on conventional oil for 20K before a switchover to Mobil 1. Used manufacturer recommended viscosity.

Your car ran 12 years and 125,000mi with Dino oil.
it can easily ran twice those numbers with dino oil
Some people think they can extend the oil change interval if they use synthetic oils. That,s not true in my book.
Oil is replaced mostly because it becomes dirty. Both oils (synthetic or dino) will become dirty at the same rate.
Synthetic will normally give some additional benefits over dino either at very low or very high temperature.
I'd rather have my engine bath in frech/new dino than in dirty synthetic after 5,000mi.
jackD

This is one of the well argued points of oil talks. How much more milage can you get out of synthetic. From a lubrication standpoint sythetics will hold thier lubracating abilities much longer than petro based oils will. So from this point it may be possible to get an extra few miles out of it. I used to do a change with petro oil at 3000 but now do a filter at 3000 and the oil at 6000. Since the factory recommends changing petro at 7500 anyways I think I stilll have a good margin of safety. And since we are on the topic you said you were using Mobile one which is good but as a general warning do not touch Castrol Syntec. Where as Mobile one is a Class 2 Castrol is a Class3 and has been argued to whether it can actually be held as a viable sythetic at all because of its use of oil-byproducts known as waxes. The Redline stuff is the best but also $$ being around 9.00 a bottle however my friend with a BMW(standard) uses Redline Tranny fluid and now swears by it.

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88 300E
03 911 C4S
2008 Triumph Speed Triple

My pics --> www.BrettAdamsDesign.com

Mike: How's the car doing? What prompted the head job to begin with?

I also had a new valve job done to my wifes '88 300E. BTW what a difference... anyway, the mechanic who did it works for the local MB dealer, very respectable and very knowledgeable guy. When I ask him about the oil, he said he put in Mobil1 0/40. The car has about 175,000. It's been 8 weeks since the job and everything is dry.

When I asked him about the 3000 vs 7500 he basically said that factory recommends the 7500 because they have not seen any significant dirt deposits assuming the engine has been taken care of. If you took care of the engine then it is better to have the much cooler synthetic vs. the dino oil.

Now it is time to do the '92 400E, with 211.000 but he said the car does not need anything. I guess I will have to trust him.

I switched the 260E over to synthetic at 184,000, it now has 302,600 miles and no leaks. I use oil, but don't leak it. I also switched to Mobile 1 0W40 for the upcoming winter (or lack of) and my consumption went from about 850 miles per quart to 1,500 miles per quart. Go figure.

Interesting about Castrol, I just bought 2 cases!

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Brian W.

01 S55 AMG Silver
01 CLK55 AMG Silver

My '92 300TE saw exactly as described in several posts "cleans some varnshing, etc. off the seals = some new leaks and then none after the seals swell" Leaked a bit for 2 changes and now virtually dry

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David
1986 300E Anthracite + ECodes + MB Mileage Award

Mike,

Do yourself a favor and run a real Synthetic like Redline or Amzoil in your Mercedes (for sure in your long service interval components like rear axle and trans). Castrol Syntech and Mobil 1 are both really good oils, but not truely synthetic as far as I'm concerned. Its been quite a hot topic on the Forum.

More info about synthetic than you need:
http://www.peachparts.com/shopforum/showthread.php?t=30429
and
http://www.peachparts.com/shopforum/showthread.php?threadid=31001&perpage=15&pagenumber=1

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Thanks,
Dave

1998 BMW 540i Sport
1995 E320
1992 400E
1989 BMW M3
1979 Triumph TR7 (1st car)
1986 BMW 735i (Sold)
1980 BMW 320i (Sold)