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Comment by boomboomsubban | Hacker News Reader

Why does the article only mention the mpg the older cars get? A significant number of the new ones use gas, do they perform better? I somewhat suspect not given their size.

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The internal combustion engine (ICE) variant has an estimated fuel efficiency of 14.7 mpg‑US (16.0 L/100 km), decreasing to 8.6 mpg‑US (27 L/100 km) when the air conditioning is on. For comparison, the earlier LLV (built 1987–94) and FFV (2000–01) have an average observed fuel consumption of 8.2 and 6.9 mpg‑US (29 and 34 L/100 km), respectively.

https://en.wikipedia.org/wiki/Oshkosh_NGDV

Wow, that is a massive hit to fuel consumption from the A/C. What gives?

Is it? The thing's huge, air conditioning is never cheap. A quick search says average cars consume ~25% more gas with AC, making it somewhat high.

I think short trips at low speeds are also terrible for AC, dunno how they did the projections.

my car consumes 5% more with AC on. it's a 2002 Mazda. So, I don't believe 25% number.

I feel the same way. I've never had a vehicle that consumed more than 5% extra with A/C. With my current diesel I can't notice a difference at all.

My source was a government site, make of it what you will. I may have worded it more strongly than I should have. https://www.fueleconomy.gov/feg/hotweather.shtml

Consumer Reports did a study on this and it only reduced gas mileage by 3% on a Honda.

https://shop.advanceautoparts.com/r/advice/car-maintenance/c...

At 65mph and ~85 degrees. The page I linked sources several studies testing at many other temperatures and speeds.

No car takes a 25% hit from the A/C in gas mileage.

>The internal combustion engine (ICE) variant has an estimated fuel efficiency of 14.7 mpg‑US (16.0 L/100 km), decreasing to 8.6 mpg‑US (27 L/100 km) when the air conditioning is on.

It may be a “worst case, only when actively cooling at maximum power” figure. In reality you’d expect ambient conditions to make a big difference to aircon energy use.

No. Sorry the quick search result was dead wrong.

A quick search says average cars consume ~25% more gas with AC, making it somewhat high.

Tons of websites say this but in my own testing during my commute the difference is almost unnoticeable, let alone a full 25%.

I think the numbers here are more like the expected consumption in actual mail delivery usage vs. something like the familiar EPA MPG ratings you'd see on cars.

A mail truck is going to be driving pretty slowly and stopping a lot, both of which will make an extra constant load like AC have a bigger effect.

Perhaps you can't use the auto-start/stop feature of the ICE system when the aircon is on? When the vehicle is stopped, something needs to be turning the compressor or things get hot pretty quick in hot climates. USPS trucks probably benefit from the start/stop system more than any other efficiency feature this new vehicle has.

AC ON with door open venting to the outside at all times, no air dam.

As a european, I am baffled by those numbers ! A 2.0L consuming 27L/100 is MASSIVE.

I have a 2 ton car with a 1.5L turbocharged engine, and even with air conditioning and city driving it NEVER jumps over 7L/100.

I always find the gas mileages of american cars just mind boggling compared to those sold in Europe

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