Better mileage going 65 than 60?

[Jonathan_ED3]

This is in a '93 Civic 2dr DX 5spd, all stock...

I've noticed the past few tanks that I'm getting better mileage going 65-70 than I do going 60mph. I've been speeding lately because I seem to always be running late to school or work.

Additionally, as I look over my gas log, most of my tanks where my mileage is on the higher end of the spectrum, I note that I wasn't driving efficiently, I was speeding everywhere and/or generally driving like a maniac, sitting in traffic, go through drive-throughs. Yet when I baby the car, drive no faster than 60mph, don't sit through any drive-throughs, my mileage doesn't seem to increase.

I guess this is exactly why a SuperMID is vital to have. I will definitely have to try to get one at some point.

Has anybody else noticed anything quirky like this? Until my mileage shows otherwise, I'm going to start speeding!

[StorminMatt]

You just have to love the way that people tend to take a 'one size fits all' approach to improving fuel economy. But the truth is that this almost never works. Every car is a little different. Drag coefficint is NOT a constant, and can actually DECREASE with increasing speed over some range(s) of speed. And it is also quite possible that your engine (like SO many Honda engines) is just not very happy cruising at low RPMs. So you just have to experiment to see what gives you the best mileage. Because you can't take it for granted that it will ALWAYS be in the 55-60MPH range.

[theholycow]

Enjoy it. Drive faster than other GasSavers.org members.

How many RPM is 70mph for you?

Can any other ~1993 DX drivers chime in with their own results?

[aalb1]

In for this. My last tank was my best tank yet pulse and gliding 50-60mph. On this tank I had the opportunity to P&G 45-60 on the first quarter tank and it seems to have gotten worse. Slower is not always better.

I wish I can have some sort of fuel instrumentation too but it's not happening on my car any time soon.

[palemelanesian]

Sort of the same car. Mine is a 96, so it's got the 1.6L engine instead of 1.5.

Some examples, on the same 150 mile route:
P&G 60-70: 55 mpg
P&G 50-65: 63 mpg
P&G 45-60: 67 mpg

This is with heavy use of pulse-and-glide. In some cases, on hills for example, a lower limit of 45 is too low for p&g, and 50 will be better. However, the upper limit can't get too high or mileage will start dropping off. Above 60 is too high for the best mileage.

[theholycow]

Originally Posted by aalb1

I wish I can have some sort of fuel instrumentation too but it's not happening on my car any time soon.

There are options, but none of them are as easy or as nice as the ScanGauge. Check out the DIY fuel rate meter link in my sig.

[palemelanesian]

One more thing:

For a test, one time, I did a straight, nearly flat segment at 15-30 mph p&g, driving like I was in a competition. 85 mpg.

[aalb1]

Originally Posted by theholycow

There are options, but none of them are as easy or as nice as the ScanGauge. Check out the DIY fuel rate meter link in my sig.

^^ Yup I got that. It was helpful but still very limited. I have Honda's DPFI system it uses 2 different sized injectors and it's confusing as hell and seems completely random.
I was able to confirm that at steady throttle I get the same FE at 50mph and 55mph. 60mph and it starts to go downhill.

[palemelanesian]

Check out the MPGuino project at ecomodder. It might work for you.

[1993CivicVX]

I drove a '94 Civic DX Coupe to 52.5mpg over a 500+miles tank. I was babying it. I did go 70mph briefly on the highway, but i think I was mostly doing 65 on the highway. I didn't know about P&G at the time, although I did some toward the end of the tank. I've had a few instances where my mileage didn't increase when I babied it more.... There does seem to be an ideal acceleration rate and cruise rate for each vehicle. But what you are describing doesn't really make sense. Describe what you mean by driving like a maniac. And describe what babying it means for you. If you are accelerating too slowly and never getting up to speed then that isn't good either. What RPMs do you shift at when babying it? What RPM do you shift at when driving like a maniac? Idling really doesn't use that much gas.. so it's more how you are accelerating and how much you are breaking that has more impact on mileage than whether you idled through a few drive thrus during the course of the tank.