Geo

Oh for sure. Even more so for the elevated cylinder pressures which would tend to put more combustion gases in the crankcase, and thus the oil (very bad). Also, the more highly stressed the engine, the more often the oil should be changed. I will change the oil on my race car dramatically more often than my road car. One has to take into consideration the engine and how it's being used.

StoogeMoe

Well I just switched to that new Mobil 1 15w50 oil. So far I have 1500mi on the change. Getting it to last 15k miles would be great. I'm going to keep an eye on the color and see how it changes over time. We do have oil coolers that extend the oil life anyway, so I will try.

I think the manufacturers do play on the insecurities of car owners. What's that new Castrol commercial that implies that the Mobil 1 claims are ridiculous and say you should change your oil every 3000 miles. They list harsh conditions for your vehicle - short trips, highway speeds, and stop and go driving. That doesn't leave much else. These are the same guys pilfering us out of $2.00 a gallon of gas.

seb928s

The color of the oil has nothing to do with the condition of the oil. I work with oils everyday. You can take that sample mail it off and it will still be like new oil after 7k. If you guys really want to know what is going on send it off after whatever miles you drive and see what the lab finds. Yet still we write the sticker for 3k unless I know the person and they understand oils a bit. The 3k stuff is bunch of bs and that's it.

Serge944

Change the filter every 3-4k and the synthetic oil every 6-8k. Most people change their expensive Mobil 1 every 3k, which is completely unnecessary. Don't get me wrong, I used to do the same... If the oil isn't dark, it is still good.

Also, the 15k oil changes are completely bogus. Many vehicles are having their engine warranties voided (particularly hondas) because of oil sludge build up. Read the disclaimers, 15k is only good for 100% constant freeway driving on a cool day.

Bryan Welch

Where are good places to send used oil for testing? Is the test very expensive?

CurlyDE

http://youroil.net/

Imo000

Everyone should stick to the manufacturer's recomendations and not what the oil companies say.

Why is it so hard to just read the owner's manual and stick to that interval? Instead trying ot debate something that only a few people have insight to. Dark oil has nothing to do with it's condition. Diesel engines get there oil black in less than 60 miles..... yet the interwas is 15000km.

Feeling the oil for cleanliness is also another no no. If you can feel the particles in the oil, then the filter is not working and the engine is probably too damaged for an oil change to make a difference.

Oil gets diluted by fuel vapours contained in the blow by. Every engine consumes oil. How do you think the compression rings get lubricated????? The amount of consumption varies from one auto manufacturer to anther.

It's the rate of consuption what makes it visible. If the rate is higher than what the blow by can replace, the oil level drops. Used oil is alway thinner than new. This is cased by the amount of fuel diluted in the oil. There is no such thing as " my car desn't burn a drop of oil" It does, you just can't see it.

Heavy duty use is city driving and short trips. Highway driving has alot less effect on oil than city (stop and go) driving.