Sorry for the stupid question, but does adjusting the valves have any affect on fuel mileage? And, how do you know when you need to adjust your valves?

Thanks in advance

Charlie

PS. How do I add that my car is a 300D?

I suspect that anything that effects how your engine runs will effect fuel mileage.
Adjusting the valves is a maintenance item. I forget the interval. It's in the manuals and the archives if you care to search.
Or I'm sure someone will post the exact interval.

Go to USER CP then SETTINGS & OPTIONS.

The THREAD TOOLS is a good option to know about.
When you open a thread you'll see it on top. Then you can subscribe to threads that interest you and pull them back up quickly and easily in the USER CP.
You can also print them out and save them. Buy yourself a binder and save them in sections.

Danny

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1984 300SD Turbo Diesel 150,000 miles

OBK member #23

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1. Adjusting the valves to the correct specs does increase fuel mileage, your gains are in direct correspondance with how out of whack the clearances were prior to adjustment. You're not actually making the car get better mileage than it's intended to, just putting it back where it should be.

2. I've heard as often as once a year. Once you get the wrenches there is no $$ investment to doing it, just $10 for a new valve cover seal. Also get a 27mm socket for the balancer bolt with a 1/2" drive socket wrench and a 1" extender to turn the engine over by hand or use the starter. I did that my first time and it works pretty well once you practice it on the first few valves.

3. Do it with the engine cold, or you'll mess up your clearances.

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"I would rather be ashes than dust!
I would rather that my spark should burn out in a brillaint blaze
than it should be stifled by dryrot.
I would rather be a superb meteor,
every atom of me in magnificent glow,
than a sleepy and permanent planet.
The proper function of man is to live, not to exist.
I shall not waste my days in trying to prolong them.
I shall use my time."

-Jack London 1876-1916

1983 300CDT (running WVO since 12/05)
1981 300SD (parts car)

The people who made your car...and wrote the manual .... suggest setting them every 15,000 miles...
Learn to set them correctly... if you accidentally get them too tight...you can burn a valve... which means taking the head off to fix the situation..
Unlike old American cars... which got looser with use... an overhead cam gets ' tighter' as the valve wears into the head... so you do want to keep them set properly... and on a regular basis...

Excellent point Leathermang, also loose valve clearances would increase starting problems, cause valve float at high rpm, also cause pitting to the valve seats. Luckily due to excellent carbide tips in the OM 616/617 valve train, the adjustment intervals are quite long.

I have seen though that using good quality engine oil with proper oil change intervals do keep the valve lash at minimal and the variations are not that high.