It's interesting you say that... Synthetic oils don't necessarily last longer than mineral oils. The oil itself isn't the problem - its the detergents, friction modifiers and things that break down through heat cycles and over time. As a rule with my vehicles, they get new semi-synth every 7,000kms. When I had my last car (Direct injection petrol turbo), I changed it every 5,000. And that oil was cooked each time.

Having pulled the tops off more engines than I could count, you can immediately tell an engine that gets regular oil flushes compared to one thats run on longer intervals. Sure, the engine might last your whole ownership without having a serious issue... But inside it'll probably tell a different story.

Modern cars don't need it that often, period. Conventional or synthetic.

Parts stores still push the 3k miles/3 months (or did until very recently). Dealers and manufacturers don't, and haven't for at least 10 years.

Modern Diesels in the US have a 15,000 mile interval for oil changes.. but they still put a sticker in your window at both dealerships and oil change locations to come back in 3-5,000 miles.

My 'free oil changes under warranty' deal when I bought my truck required me to come in every 5,000 miles. Their computer system was setup for cars, and they had no way to change it..

My Subaru Forester gets an effective oil change every 2500 miles. It burns a quart of synthetic in that time. Too little to get the recall work done (faulty rings). But at least the car gets a gradual oil change over the year!

Is there a difference though? If you see my other reply to the parent, I posted the US oil change schedule for a european car. It seems to be in line with what I experience in europe .

Is it a difference between european and US made cars?

I know nothing on the matter, but it seems to me that it's a cultural difference. Americans are just more used to changing the oil often, so oil companies can sell them more oil even if they don't need it.

Found this http://www.autoblog.com/2009/02/24/oil-change-intervals/

"For years the accepted oil change interval (as per carmakers) had been every 3 months or 3000 miles, whichever comes first. And why was that? It was because oils of yesterday broke down when left in the crankcase environment for longer than the prescribed interval. The combination of heat, friction, and the oil oxidizing over time resulted in an unholy clothing of the engine's internal parts called sludge."

That's an absolutely insane number, and I have never heard of that (I have had cars for 20 years that always were 10k to 15k km intervals, and simply done on a yearly or 18 months service).

I have a tractor from 1939. The owners manual states that modern oils are much better than old oils and as a result practices of years past do not apply. (I don't recall the exact wording) If you ask collectors today there is a big debate on if it is safe to use modern detergent oils in those old tractors.

It's a difference in the oil used.

The standards for oil are tightly regulated in the EU.

The manufacturers are pretty picky with what oils they recommend for their cars too. I mean if I need a "fully synthetic 10W-30" for my car for example (from the manual) - and the brands are all global megacorps (Shell, Havoline, Mobil, Castrol etc). So with the tight spec and global brands surely I must be getting the same thing in the bottle here as one gets in the US?

Depends. VW has their own 'standards': 502.00, etc. Subaru theirs, and so on.

But many brands meet that spec. It's really only white label conventional bottles that don't.

Most people don't use synthetic oil.

In my case, it's cheaper to use non-synthetic oil and change it quarterly, which generally aligns with other maintenance activity. (Tire rotation, filters, lights, etc)

Here in Europe engine oil is typically always multi-grade, and often fully synthetic. I believe this is because standards are stricter here (although I can't find anything confirming this), and synthetic oil often leads to engines lasting longer and lower emissions.

This is why manufacturers have different recommendations for Europe. The formula of the oil is completely different to the US, so it can stay in the engine a lot longer.

> synthetic oil often leads to engines lasting longer

This is true in theory, but for most people the rest of the car will fall apart before the engine dies. All the rubber and plastic is degraded by air and sunlight which has little to do with any use patterns. (there are of course uses that put more wear on them as well)

A good portion of the cars are junked with so little use that they would have made it that far without any oil changes at all. Of course the oil would be like syrup, and the engine would show other signs of the abuse, but it would still be running well enough to make that last trip before the car is destroyed for other reasons.