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0 pointsits_ethan1mo ago0 comments

Right but what I'm getting at is that there can be tradeoffs that might make designing for maintainability mean optimizing for something less important to the end user.

Do you optimize an engine for how easy it is to replace a filter once or twice a year (most likely done by someone the average car-owner is already paying to change their oil for them), or do you optimize it for getting better gas mileage over every single mile the car is driven?

We're talking about a hypothetical car and neither of us (I assume) design engines like this, I'm just trying to illustrate a point about tradeoffs existing. To your own point of efficiency being a trade with durability, that's not in a vacuum. If a part is in a different location with a different loading environment, it can be more/less durable (material changes leading to efficiency differences), more/less likely to break (maybe you service the hard-to-service part half as often when it's in a harder to service spot), etc.

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manquer1mo ago

Only TCO matters, that is the efficiency you actually optimize for, ie dollar per mile[1]not miles per gallon.

If the car is going to need to be in shop for days needing you to have a replacement rental because the model is difficult to service and the cost of service itself is not cheap , that can easily outweigh any marginal mpg gain .

Similarly because it is expensive and time consuming you may likely skip service schedules , the engine will then have a reduced life, or seizes up on the road and you need an expensive tow and rebuild etc .

You are implicitly assuming none of these will change if the maintenance is more difficult , that is not the case though

This is what OP is implying when he says a part with regular maintenance schedule to be easily accessible.

[1] of which fuel is only one part , substantial yes but not the only one

quickthrowman29d ago

> Only TCO matters, that is the efficiency you actually optimize for, ie dollar per mile[1]not miles per gallon.

You’d be surprised how few people actually consider TCO when looking at vehicles, the amount of people driving Jeeps and Audis and similar vehicles that depreciate 60-70% in 5-6 years blows my mind, I just assume anyone driving a car like that hates money.

I bought a RAV4 for $32,000 in 2021, a co-worker of mine paid just over $60k for a Jeep Grand Cherokee 4xe the same year, and the model years are the same. 5 years later, my car is worth more than his (around 22k, his is 18-20k), he ate over $40,000 of depreciation in 5 years, that’s just insane to me.

its_ethanOP1mo ago

I'm just gonna copy and paste a response to another similar comment:

The point that I am making (obviously, I think) is that tradeoffs exist, even if you don't think the right decision was made, your full view into the trade space is likely incomplete, or prioritizes something different than the engineers.

Putting some random number of hypothetical mpg improvement was clearly a mistake, but I assumed people here would be able to get the point I was trying to make, instead of getting riled up about the relationship (or lack thereof) of oil filters and fuel efficiency.

manquer1mo ago

I did read that before commenting, to be clear - the specific nature of your proposed optimization is not important and I took your premise to be true ie it will improve fuel efficiency and therefore save some money.

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In general, the point was it is not operational efficiency in ideal conditions alone and serviceability is an important component because it can add to the overall cost of ownership significantly and individual car owners (in comparison to fleet) are typically poorer in factoring this in their buy decisions.

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It comes down to numbers , if the proposed change, results in 10% improvement probably not worth it, 10x then definitely so .

I.e will the car become 22 MPGe or 200MPGe . Larger the gain more trade-offs like serviceability or life expectancy all can be sacrificed.

hybrids costs more upfront (both sets of expensive components - transmission/motor +engine/battery) but still work if driven enough miles, as the gain in efficiency makes up for the upfront.

Exact number of that miles is localized to you and me - depends things like tax difference including tolls, gas prices, MPGe diff, electricity prices, interest and purchasing power of currency other consumables costs like tires and so on.

j / k navigate · click thread line to collapse

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manquer1mo ago

Only TCO matters, that is the efficiency you actually optimize for, ie dollar per mile[1]not miles per gallon.

You are implicitly assuming none of these will change if the maintenance is more difficult , that is not the case though

This is what OP is implying when he says a part with regular maintenance schedule to be easily accessible.

[1] of which fuel is only one part , substantial yes but not the only one

quickthrowman29d ago

> Only TCO matters, that is the efficiency you actually optimize for, ie dollar per mile[1]not miles per gallon.

its_ethanOP1mo ago

I'm just gonna copy and paste a response to another similar comment:

manquer1mo ago

—

——

It comes down to numbers , if the proposed change, results in 10% improvement probably not worth it, 10x then definitely so .

I.e will the car become 22 MPGe or 200MPGe . Larger the gain more trade-offs like serviceability or life expectancy all can be sacrificed.

hybrids costs more upfront (both sets of expensive components - transmission/motor +engine/battery) but still work if driven enough miles, as the gain in efficiency makes up for the upfront.

j / k navigate · click thread line to collapse