Johngray,

It seems to me that most of the people I hear recommend 3,000 mile oil changes are in the auto repair business. They see the results of lacadaisacle(sp?) oil changing. They also are in a business where neglected engines bring them more business, but they point out the advantage of frequent oil changes anyway.

If you drive a few thousand miles a year and trade cars often, I guess you don't need to worry about changing oil very often. If you drive a lot and want to wring the most out of your engine, it's difficult to change it too often.

Also, the main advantage to high quality oil, is the care and attention paid to additives. The cheaper brands don't have additives in as much quantity or quality to keep the inside of your engine clean, as well as other important things. If you use cheap oil, you could probably do quite well with it, if you were to change it often. Quality oil, changed frequently is proven to be the best engine insurance.

Good luck,
Change oil hot, and change oil often,

------------------
Larry Bible
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

SOME OLD INFO ON OILS

Some years back --maybe mid 90's== Consumers Reports conducted a year long (or longer) test of motor oils in NYC using regular NYC cabs. It was a very thorough test where the engines were taken apart after so many miles and all the pertinent parts were measured by the fellows running the tests who were auto engineers not amateurs.

The results were very interesting: no real difference detected between any of the American made oils that they used.
Also, they tested the belief that 3k is the magic number. No discernable change or variation found between 3K and 7 K oil changes.

The test was a 100K miles span in American made engines used normally (strange term in this city) on the streets of New York City summer and winter. Summer is hell here for any engine, particularly, if you have to hassle for a fare. By the way, taxis cannot be older than 3 years old by law.

Also, synthetic oils did not produce any tangible difference either.

JA

Actually, Taxis may not be a good test bed for oil change intervals, here's why;

Taxi's are started in the morning and run virutally all day long, maybe even 24 by 7 with different driver shift changes. An engine that doesn't go through a lot of warm up/shutdown/cool off/startup.......... cycles does not go through as many of these cycles in a given number of miles. One of the problems is moisture and acid build up, this is what the additives in the oil try to fight. The typical engine situation would produce much higher acid and moisture deposit amounts.

The worst possible scenario for an engine is someone who starts the car every morning and drives it a mile or so to the office. Starts it that evening and drives it a mile or so back home. That's why it's common to see recommendations of X miles or Y months whichever comes first.

The test you cite is a very interesting one, I'm sure it would be much more difficult to perform such a study on cars used in typical service. It would take years, the taxi test probably took months, or a few years worst case.

Thanks for the great information,

------------------
Larry Bible
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

These "oil" threads seem to draw alot of comment. Oh well.

Larry Bible and I subscribe to the same school of thought - change it often and ABOVE all, change it HOT.

I'm not a Benz expert, but I have taken 2
inexpensive Japanese cars to 550,000mi.
I live in south Texas and run a good 20W-50 dino oil. I tried the "mostly" dino and "partly" synthetic thing in the Benz awhile back and the oil consumption went up.
I experienced oil loss also in a '95 Isuzu Rodeo using pure synthetic. I'll never use synthetic again. I change the oil in my Benz every 1,500 mi. and I do so when it's HOT.

I realize alot of folks prefer synthetic and I'm NOT trying to stir up a fuss, just expressing my opinion.

CHANGE IT OFTEN - CHANGE IT HOT.

I've been doing this for 35 yrs. and it's served me very well.

Regards,

Mike Murrell
'91 300-SEL