Fuel Mileage Report

[Pro03]

A few weeks ago I posted about poor fuel mileage in my '03 LX. I was only getting about 25 mpg highway. Of course, this was my first highway trip. I was running bewteen 75-80 mph most of the way. On the exact same trip this time I got 32.22 mpg going 65-75 mph, but mostly between 70-75 mph. Since the first trip I've had the start-up rattle TSB done which did involve some recalibration. Other than that the car was the same. Same oil, same tire pressure, same octane, same everything. In fact, this time I ran the A/C about 50% of the time and had a strong sidewind for a while. The only thing I can attribute the change to is driving style. The first trip I was driving faster, in more traffic. This time was less traffic and I held the speed down. What a difference! (eekdance)

[SciFiMan]

Yes, after you pass 65mph or so, there is a increasingly big hit on mpg. Something on the order of 20 percent. It takes about 12 to 15 horsepower to keep the car cruising at a constant speed of around 50. As wind drag increases so does the ponies needed to maintain that speed, thus sucking more and more fuel. I don't know if the increase is linear or not.

[iluvmacs]

Another reason is that at speeds between 65 mph and say 80 mph the protege engine is operating at it's torque peak. If you look at a dyno sheet you'll see that at those speeds the engine is making it's most torque. It happens to be running at peak volumetric efficiency, but that's not what gets you highway mileage.

If you drive a honda on the highway you'll notice a severe lack of torque below 80 mph. This is because the honda engine (my old civic, may not apply to all hondas) hit's peak torque above 4000 RPM, which is around 80 mph. The less torque your engine has, the better mileage you get. Drive 200 miles with 80 ft lbs compared to 130 ft lbs and you'll notice a huge mileage difference.

I garauntee that the difference in fuel mileage between 60 mph and 70 mph is much greater on the protege than on other cars because the engine efficiency dominates air resistance at those speeds.

Fix: get a new final drive ratio
Fix: get radical cams that make power between 4500 and 6500 RPM

[Pro03]

It's funny that you mention Hondas in comparison. I've owned 4. My '99 EX coupe got 35 mpg on the same run and my '02 EX coupe got 37 mpg - and it was auto! I'm pretty sure drag rises as a square of speed, so it should be linear. But then again there's so many things that can affect drag and thus mileage. I did drive with a front mask, so I wonder if that affected milegae any. I posted about this before but we never came to a real conclusion. In any case I'm pretty happy with 32 mpg from my Pro. I was worried there for a while. But there's no denying that Civics get better fuel mileage. But there's pros and cons to each car.

[03promaz]

I get 30-32 dong 80 driving back and forth from Tucson, AZ to Denver, CO

[Pro03]

The more I think about it the more I think that my car just hasn't broken in yet. It hasn't yet hit 7k miles. I've read other posts about fuel mileage improving over time. We'll see.

[Protege52003]

i get 30 mpg doing 75-80 MPH on the highway taking it easy!

[Mike R]

I've never gotten more than 28mpg on trips. No matter what the driving style. Yeah, hondas rock. I get 38-49mpg with the 94 civic- bone stock!

[manofmacg3]

I did an 800 mile trip.. going bout 75-80 whole way... had about 12,000 or so miles on car.. i got 29mpg. I have no idea what i get now.. i should start paying attention to my city mpg.

[Marik123]

I have a 2000 1.6L auto 53k with K&N air filter. Filled up with 87 Chervon gasoline

City 28-32 MPG
HWY 35-40 MPG

For city I get alot of stop and go's but the MPG min at 28 MPG, seems descent for 26City/33HWY for the vehical. But one thing for sure, I dont do any aggressive driving and usually feather on the gas. Driving style DOES make a difference to ur MPG. But I think that civic save more gas maybe because it has either 1.6L or 1.7L engine vs Protege's 1.8/2.0L engine...