I have a 2013 base fit automatic. If i were to drive on a fairly flat highway on cruise control what fixed speed(mph) would give me the best mpg for my car? thank you

 

If I remember correctly, the best MPG comes at the lowest RPM of the highest gear, which in the fit, i think is like 35mph. But on the highway, with the Fit, the slower the better is from my experience.

 

We have gotten 40 MPG twice at 65 MPH, with cruise control on as much as possible. '13 Fit with 5 M/T. I think RPM is around 3300 at that speed. I wish I had a 6 speed, cuz it would lower RPM, but I think the little engine is kinda loafing at 3300 RPM. Mind you this is on Arizona back roads, where speed limit is 65. If you go on the main hiways, it's 75, and MPG kinda goes out the window. Haven't yet driven at that speed to go somewhere, so am curious as to what the MPG would be; probably over 30 something.

 

With an automatic, whatever is the lowest speed it'll do in top gear. In my Odyssey that's 45 mph.

With a manual, slower is better all the way down to idling at 25 mph in 5th gear. This chart is from my own testing with a calibrated Scangauge, average of 2 runs (1 each direction) on a straight flat 2-mile stretch of road, cruise control to hold speed. 25 mph is the lowest speed cruise will hold.

 

25 MPH in 5th gear???? Wouldn't that lug the engine? I try not to drive under 2000 RPM in any gear. I can drive at 35 MPH in 5th with little problem, altho it feels like the engine isn't too happy there. 40 MPH in 5th is better. On my way to work, I drive part fwy and part surface street, and try to get into 5th as soon as I can, but also don't wanna lug the engine. Fine line, I guess.

 

I got 42 mpg at a steady 55 for most of a trip, and that was fine.


Keep in mind how little money you might save going from, say, 42 to 52 mpg, vs how much more time you'd waste driving 40 mph instead of 55.

 

Even if you have the time, safety should be number one, saving money two.
Speed is regulated on all highways, problem with finding an optimum slow speed is the majority of drivers have a mind set that the limit is the least you should drive and anything slower you are in their way.

 

I'm not telling anyone what they should do. I'm just telling the numbers. There's a time and place for everything, and a time and place to avoid certain things.

25 mph in 5th gear is pushing the limit, but I did it to get the full set of data.

 

I've made the trip from Kansas to California a couple times in my '09 5 m/t running about 65 or 70 at 3300- 3800 rpm and got roughly 42- 48 mpg with a/c on.

 

Did you have its ECU reflashed?

 

No ECU reflash, just full exhaust and customs cold air box and intake at the time. Also watched the tire pressure like crazy.

also forgot I had the final drive regeared

 

I'm afraid that was a bit of a trick question.

The 09 Fits have a data error that results in the average mpg displayed being 10-15% higher than actual.

You might want to have it updated. Honda shouldn't charge for this (there's a TSB on it in the sticky thread at the top of this forum). It doesn't change the car's performance in any way. At the same time check to see the Lost Motion Spring (LMS) recall was done.

 

I've never listened to the crappy average mpg display. I do it the old way total miles/ tank size = mpg, works better and its more reliable. I drive the car about 200 plus miles one way daily to and from work so I've done everything I could to get the best mileage.

 

but I've retired her from daily duty and she's going to get a refresh for track duty

 

ok cool. But I think 48mpg @ 65mph+ must have had a good tailwind. And going downhill.

 

Agreed. My test shows about 40 mpg at 65 mph.

Mine's an 09 and has not had the fix. It reads about 12% high, so it would show 45 mpg at 65 instead of 40. I have my calibrated Scangauge so I don't care that it's wrong.

 

My OE gauge is actually conservative. It reported 41.0 on my last tank, but the pump said it was 41.5.

 

The problem was specifically 2009 models. They fixed it for 2010.

 

48 mpg at 65 mph. No way!!! Come on, get real. At 65 mph your lucky to get 35/37 mpg. I think mpg embellishment is a big problem here at FitFreak.

 

With a properly geared trans and carefully monitored tire pressure and a few intake and exhaust mods, that and if you keep your foot out of it which most people seem to have trouble doing. That and a manual always gets better mileage then an a/t