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Should I change my BMW's oil even if the quality indicator doesn't say so?

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My Z-3 has oil quality indicators (green bars). Since I drive the vehicle few miles I may go two years before the indicators show that the oil should be changed. My mechanic, who is very trustworthy, said that the indicators only show viscosity quality but that there are important additives and other chemicals that break down in about a year and that the oil should be changed, at minimum, annually. I don’t want to overdo the oil changes but don’t want to harm the engine, either. The vehicle has 158K miles.

Impossible to overdue oil changes. You mechanic is correct (mostly.) The oil should be changed once a year. The bars have nothing to do with oil viscosity, they show when the oil should be changed based on how you drive. That said, they apparently don’t have a calendar built in. Some cars do, some don’t.

If you check you owners manual, I’d bet there is a sentence in there to follow the indicator lights OR every year, whichever comes first.

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Heh heh, yeah why spend an extra $70 a year on a oil change on what, a $50,000 plus car? But hey, let us know how it turns out.

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More like $5000.

Well gee why bother changing oil at all then?

I wish all my cars did onboard oil analysis.

I wouldn’t trust a mechanic that thinks the car actually monitors oil viscosity.

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OK, let’s be clear here, the oil indicators are only a computer program. It has no idea what the oil is like. You could put in maple syrup (very costly though) and it’d still think the oil was ok. True though the manufacturers claim the program is based on much research. So it’s just research vs experience vs caution vs the cost of error vs just wanting to take care of stuff.

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But the research documents the experience of the BMW engineers as they tested different parameters the oil life monitor checks. I have a hard time imagining a car company in good financial shape doing anything that would endanger the profitability of that company. The only time I can recall this happening is the VW diesel fiasco, and they paid a steep price for it.

I’d be more concerned with the mileage interval than the time myself. 5000 miles is when I’ve always changed oil & filter on all my vehicles and never had any oil related problems.

You can rely on the indicators but check your owners manual. It may stipulate a time period even if the indicators still show good.

The indicators are based on the driving you do. A lot of parameters go into the algorithm that determines the quality of the oil. But one factor is not programmed into the algorithm and that is the actual oil you are using. It is based on using an oil that meets BMW or European specs and not a lot of oil sold in the US meets those specs.

Unless you are absolutely sure the oil used in your engine meets those specs, you should change your oil much sooner. If you have no idea what oil is used, then don’t exceed 5000 miles or six months. If you know it is synthetic but not sure if it meets the specs, then 7500 miles or one year is tops.