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Question about lower speeds
It's a common saying that reducing speed raises MPG, but I typically see it about going from 70+ to 50-60 MPH. Does this still apply to sub-40 MPH (not top gear, it refuses to go up until 45+), aka city driving, or do I have to rely more on PnG to get numbers up?
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Typically, down to 25MPH or so, depending on air density, & etc. Of course, returns diminish and get lost in the noise.
Other techniques are drive without brakes, and don't slow down for corners. |
I usually increase speed to get into top gear. The point of traveling is to arrive at a destination. In my Acura, I can be in 6th gear at 30 MPH. In the Mazda, it's 44 MPH.
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Pulse and glide between lights is probably most efficient. Avoiding brakes is more important than overall speed in stop and go scenarios. In town, you need to go with the flow. You're not going to do 10 under in a 35 MPH speed zone, neither are you going to do 55 in a 30.
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I have observed that "it depends".
In my Insight, with the original drivetrain, fuel economy dropped off predictably (in relation to speed) above ~50mph. The faster I went, the more economy I'd lose. Below 50, the economy of steady-state driving would improve, but the car seemed more "sensitive" to outside factors, such as hills, weather, downshifts, needing to accelerate and decelerate, etc. Probably if there were a straight and level road where I could have traveled at 30-35mph in top gear for dozens of miles without any kind of interruption or grade change, economy would have peaked there, but I never really found those roads. In practice, rural roads with a 45-50mph speed limit were peak. In those conditions, the car would reliably deliver 90-100mpg on a warm summer day. I have observed a similar pattern in my MX-5. Above ~80kph/50mph, economy drops even more sharply than it did in the Insight, likely because the car is less aerodynamic. The fuel economy display is far less granular, but it appears it would get phenomenal economy at lower speeds (it goes into 6th around 50kph/30mph). However, anything less than 80kph roads in-practice result in lower economy, because they tend to have stops, turns, yields, hills, etc. which hurt far more than the lower speed helps, even using good driving technique. The car will get (in freedom units) ~40mpg at 65mph, ~48mpg at 50mph, and might get 50mpg+ even crawling in traffic in 2nd at ~1200rpm, but the moment I need to accelerate and decelerate, that economy tanks, and I'm averaging ~35mpg city. |
Steady state isn't how you maximize fuel economy in an ICE powered vehicle. Pulse and glide.
You want to avoid minimal throttle positions. I still don't like the question, because participating in traffic dictates the operating parameters. |
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For instance: Steady state driving at various speeds Pulse and glide, engine on or off Idling fuel consumption (and minimizing idle) Stop and go traffic vs vehicle weight And then there's a discussion of driving technique, and where it places your vehicle (chosen) and route (also chosen) within these conditions. The Insight was basically at ~75% load in 5th on level ground, and did not benefit measurably from engine-on pulse and glide. Proper EOC requires a kill switch, which places it as a more advanced driving technique. Neither really applies to automatics. The MX-5 has a very high compression ratio and runs deep Atkinson-cycle, which pushes the middle of the peak BSFC island much lower in the load range - closer to 55%. It's very easy to drop into fuel enrichment or deep timing retard. I'm of the opinion that steady-state driving is still pertinent to discuss, even if it's rarely the most efficient technique. My driving isn't always to burn the least fuel, or spend the least money, or make the least pollution, though these are interests of mine. |
I got 71 mpg steady state driving here in Utah today at around 74 mph on the highway. Just flexing
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My company CX-5 is getting mid 20's lately. I'm sure something is wrong, but since it's not my car and I don't pay for the gas, the motivation just isn't there. No CEL. I think it smells rich when it starts up, which is kinda normal, but it seems more rich than it needs to be.
The CX-5 gets great reviews, but I just don't see the appeal. It doesn't handle as good as a Prius or any sedan. It doesn't have any more space. It doesn't get good fuel economy. It's a very basic car that sits a bit higher than a sedan. I don't hate it, but there's nothing I love about it. |
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So say in the US, two lane flat straight road daytime light to medium traffic great weather, 60mph speed limit, how slow can you drive before becoming a nuisance/blocking traffic? Two days ago I made a trip around NW side of Lake Okeechobee SB Hwy 78 (40? miles), with lights on, ran on cruise control at 51mph, stayed to right to allow great vision for passing by other drivers. Many cars passed without even slowing down, others tailgated nearly for miles, and finally passed me after we were both passed numerous times. I get it, some people cannot pass. How much responsibility do I share here, while saving gas? |
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Have fun doing pulse and glide on an Idaho interstate going 85 mph lol. Gonna feel like you’re playing that old phone game “ flappy bird” with your feet
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