[chrisseaton]

So why don’t the manufacturer recommend it? Especially since it’s comprehensively warrantied for seven years so entirely their problem?

Either 5 is justified by engineering or 20 is? One of them must be some kind of misrepresentation?

[aronpye]

I used to help develop Diesel Engines before I moved into Software Engineering.

If they followed anything like what we did, they would just run load cycles on the engine in a test cell to simulate approximately however many miles of ‘normal’ use they want to validate the engine up to. During the testing the engine would be maintained, fueled, and oiled according to the maintenance schedule and customer guidelines the engine will be sold with.

After the testing, the engine would be completely broken down and analyzed. If there weren’t any signs of abnormal wear then the engine would be considered validated __under those conditions__.

The problem is when real-world use deviates from the testing conditions. Which is pretty much always. Then the manufacturer guidelines no longer apply.

If you run your engine harder than the test cycle load factor, you will need to replace the engine oil more regularly. If your fuel quality is crap, i.e. has any ethanol in it, you will need to replace your oil more regularly as fuel eventually gets into the oil, and ethanol results in high water content in fuels, and hence oil, which will break down seals as well as reduce overall lubrication.

If your engine breaks down due to poor oil quality from lack of regular inspection and replacement, then as a manufacturer I’d be very resistant to paying out on any warranty claim. Even if you followed the “guidelines” for oil changes, you still have a duty to inspect the oil regularly, both as a responsible driver and under the car manual guidelines. Using bad oil and / or fuel is very easy to test for.

Long story short, the oil change intervals guidelines are just that, guidelines, and real-world use dictates the maintenance schedule. Frequent oil changes, before the oil breaks down / becomes crap, is just a quick, cheap way to prolong the life of your engine or any mechanical device with bearings or sliding surfaces for that matter.

[Dah00n]

>If your fuel quality is crap, i.e. has any ethanol in it, you will need to replace your oil more regularly

That is real-world use in most of Europe and is included in the higher mileage between oil changes compared to the US discussed here. I don't even think most Europeans inside the EU have access to ethanol free petrol? At least around here (Denmark) it would be illegal. If a car breaks down because of ethanol in the petrol it is of course covered by the manufacturer. Otherwise they might as well state "warranty 5 years but not if petrol has been added at any point".

The manufacturer specified intervals are just fine and you'd need to be an extreme outlier to have any problems with your oil following them. Maybe if you have a caravan attached at all times or drive off-road or racing or all of the above at the same time. Otherwise consumer law would mandate the manufacturer pay for any damages caused, as it damn well should. It is also the manufacturer that would have to prove the fault is yours. Not possible if the car have been serviced even if done by a third-party shop. The oil would have to be visible damaged even if looked at by a granny (they cannot demand you understand oil better than "it looks like oil and is inside the specified mileage").

[chrisseaton]

> Even if you followed the “guidelines” for oil changes, you still have a duty to inspect the oil regularly, both as a responsible driver and under the car manual guidelines.

No this isn’t true. I check my oil as regularly as the manual tells me to, which is every two years. That’s literally the published inspection schedule in the UK for this car. If that isn’t regular enough and the engine wears that’s a warranty issue covered by the manufacturer.

[aronpye]

Most manuals tell you to inspect the oil monthly or before a long car journey.

Waiting two years before realizing your engine is drinking oil is probably reckless which wouldn’t be covered under any warranty.

[chrisseaton]

You mean literally checking the dip-stick? Yes they do recommend to do that more regularly, but if you mean dumping the oil out, they don't.

[Dah00n]

No consumer law would uphold that. Your 80 year old granny have to be able to see something is wrong with the oil by looking at the dip. Demanding anything else is requiring someone educated look at it which won't hold in any court in the EU.

[throwawayboise]

Maybe the oil sold in Europe is more uniformly higher grade?

If I go to the local auto parts store here, I can spend ~$1.00/qt for oil or more than $10.00/qt for oil. Guess which oil most people will buy?

Also I don't really have any confidence that the dealers are using factory specified oil. I think they probably use the cheapest bulk oil they can buy. That's why I change my own oil, that way I know what is in the engine.

[Dah00n]

Amazing. Not only do the dealers I've used not use bulk oil (unlike most 3rd party shops) but I get the leftover (new) oil in the original metal can they used. It is definitely the factory specified oil. The specific car is part of the paint scheme directly on the can.

Seems to me reading the thread that the difference is because US dealers use crappy oil so they specify more oil changes? Or maybe it's just greed.

[chrisseaton]

A counterpoint to this is that my car is manufactured in a single plant in Europe. It ships with engine oil in it (because it's driven on and off the transport ship). So I presume one sold in the UK and the US have the same oil in, yet Land Rover will tell you to change that exact same oil in the exact same engine after 20k miles in the UK and 5k miles in the US.

[Spooky23]

There’s a weird subset of Americans who are very “passionate” about motor oil. They argue about oil filters and formulations… almost audiophile like.

My guess is the guidance is to avoid some PR nightmare.

[aronpye]

Fuel and oil quality is a lot more variable in the US, so are the environmental conditions, so you have to set the guidelines according to the minimum likely to be encountered.

[eptcyka]

Its hard to give a good recommendation as oil degrades at different rates depending on use age and weather. Lots of short and aggressive trips in the city will wear it out differently to some smooth motorway driving, mileage being equal.

[chrisseaton]

Is it really a 4x difference? And don’t British people drive more shorter trips than the US so even if that’s the case it’s also the wrong way around?

[aronpye]

Fuel and oil quality is a lot more variable in the US as it’s set at the state level, plus it’s just generally worse, so are the environmental conditions, so you have to set the guidelines according to the minimum / worst case likely to be encountered.