Gas Mileage / rpms????????????

[JJBroc]

Hi,

How is everyone? I have been enjoying my 2003 Protege5 since I bought it. It only has about 18000 original miles on it. Automatic. My question is gas mileage. I thought I would be getting over 30 mpgs with this. Not the case, I am averaging about 25 mpgs.
I drive 90% highway and drive a consistent 75-80m. 27 miles to work then 27back. Just wondering what you guys are getting for mpgs.
Also wondering about my rpm ranges. Car seems to really rev from sixty up. I added a couple of pics showing my rpms just over 3000 for 70 mph and about 3400-3500 for 80 mph. I used cruise control and was on flat highway when I took the photos.
Just a touch of the peddle or a slight incline automatically adds 2-300 more rpms.
I really am not use to an automatic tranny, this is my first one in years. Last being a '69 Camaro, my first foreign. So I have no experience with their performance.
Is this consistent with the other automatics out there????

Thanks for any input,
JJBroc

 

[ARFF]

I did a long trip; 99% Highway this summer (2500km) and I found that optimum gas mileage (stock everything -I'm still saving up to make some mods) was about 3200rpm. It was working out to about 36 - 37 MPG if I did the ltrs/km to Gal/miles conversion correctly. I was very happy with gas mileage. Hope this helps out a bit

 

[Lord_Zath]

If you want better gas mileage, slow down on the highway. When I drive on the highway, I typically set cruise at 70 (that's about 3k rpms). Honestly, if you drive 70 smartly, you'll arrive at about the same time as if you drove 80 but jammed on the brakes at every instance.

 

[Flash5]

Yea the faster you go over 70 your mpg will go down. At most do 70, I have done 34mpg almost all highway at 70 so thats a good speed to be at. But auto will get less mpg anyways so u gotta factor that in too.

 

[JJBroc]

Thanks

Thanks for the replies! Yeah I realize I could slow down a bit and get better gas mileage. But it is a traffic free highway I drive in Rhode Island and I am not to worried about be pulled over.
Guess I should try the low 70's, but I still don't see how that would make such a huge difference in mpgs that you guys are reporting.
Are my rpms vs. mph consistent with your cars???
JJBroc

 

[Erci]

Thanks for the replies! Yeah I realize I could slow down a bit and get better gas mileage. But it is a traffic free highway I drive in Rhode Island and I am not to worried about be pulled over.
Guess I should try the low 70's, but I still don't see how that would make such a huge difference in mpgs that you guys are reporting.
Are my rpms vs. mph consistent with your cars???
JJBroc

Actually, RPMs are much worse with manual. At 80mph, I'm close to 4k rpm. Same finding here.. if I keep it at 70, I get great fuel economy... go 80 and it goes down 3-4mpg

 

[Erci]

Actually, RPMs are much worse with manual. At 80mph, I'm close to 4k rpm. Same finding here.. if I keep it at 70, I get great fuel economy... go 80 and it goes down 3-4mpg

My bad.. at 80mph, it's turning exactly 3700 rpm.

 

[P-Funk!]

Wind resistance is formidable at hwy speeds and increases exponentially the faster you go. Yes - top speed does make the greatest factor for fuel economy on the hwy.

I plan my time and cruise at 60MPH....

 

[JoshP5]

The reason you're not observing a linear relationship between mph and rpm is the viscous coupling in the automatic transmission.

In an automatic, there's no direct mechanical connection between the crankshaft and the half-shafts. Rather, there are two "paddles" immersed in fluid. The engine spins one paddle, which increases the viscosity of the fluid, which improves coupling to the second paddle, which is connected to the half-shafts. This is viscous coupling.

That's why you can stop without taking it out of gear, and that's why, when you hit the gas on the highway, the engine speed increases immediately while vehicle speed increases more slowly.

In addition to generally having fewer gears, this is the reason automatics get crappier gas mileage than manuals.

Some more modern automatics have direct coupling features for better efficiency/performance.

 

[Tom03es]

Your mileage is on par with mine (also an automatic). If I set the cruise at about 83 mph on the interstate, I'll get about 23 mpgs. Most tanks of intown highway (55-70 mph) and stop n go city driving will yeild tank averages of about 24-26 mpgs. I did however just get 29.5 mpgs on a tank- still not sure how I did that.

Try playing around with different grades of gas. Try a couple tanks of mid-grade gas and see if anything changes. Try different brands too.

 

[JoshP5]

Altitude is also a big factor. I used to get 5 more mpg driving around on the Colorado Plateau (8000ft) than I did in southern Arizona (2000ft).

 

[i12drivemyMP5]

The distance back & forth to work, altitude, speed, rpms, flatness, automatic & mpg are in line with mine. These 30 mpg guys have manual tranny. Maybe if you drive 52 then you might get 28 mpg, right up until someone smashes into the back of you for going too slow on the frwy. AC or not makes no difference on overall mpg on mine. I burn regular. Plus or midgrade made no improvements in mpg.

 

[JJBroc]

good feedback

Thanks I appreciate all the feedback. Going to change plugs this weekend, they are probably original, noticeable difference?, doubt it. Haven't really messed with the car yet.

 

[Gabio]

I can bring an other reason why 3200rpm is the max you should go while on a trip.
The engine is modifing the air/fuel ratio (this or the timing, I don't remember) at 3500rpm, so you get more hp.

You can notice the change when the engine is cold. With a constant acceleration, you'll notice a little boost at 3500rpm and a change in the sound (which is even more noticeable with a CAI).

 

[JoshP5]

The afr and timing are modified continuously across the rev range. What you're observing is one of the many dips in the power curve. aMaff posted a stock dyno curve which shows it explicitly.

 

[Cellerator]

I got 25mpg doing an average of 90mph on my way home this past monday. This was a 360+ mile trip and first of the engine the insurance gave me.

 

[Typrus]

T/C Lockup's came around in the 80's....? I'd be surprised if these auto's didn't have one?

Are there any aftermarket lower diff's or swappable 5th gears? (Coming from my mom's 96 VW Passat TDI)

 

[justanothermp5]

dude i get about 30 or 25 somewhere in that range and my 2002 protege 5 has 200,000 miles on it, and yes i ment to put two hundred thousand miles

 

[Flash5]

The reason you're not observing a linear relationship between mph and rpm is the viscous coupling in the automatic transmission.

In an automatic, there's no direct mechanical connection between the crankshaft and the half-shafts. Rather, there are two "paddles" immersed in fluid. The engine spins one paddle, which increases the viscosity of the fluid, which improves coupling to the second paddle, which is connected to the half-shafts. This is viscous coupling.

That's why you can stop without taking it out of gear, and that's why, when you hit the gas on the highway, the engine speed increases immediately while vehicle speed increases more slowly.

In addition to generally having fewer gears, this is the reason automatics get crappier gas mileage than manuals.

Some more modern automatics have direct coupling features for better efficiency/performance.

(bow)

 

[JoshP5]

dude i get about 30 or 25 somewhere in that range and my 2002 protege 5 has 200,000 miles on it, and yes i ment to put two hundred thousand miles

Sorry to go off-topic, but how do you like your Tanabe/HP setup? You have GF210s?