So, what *really* makes for good interstate fuel economy?

Wow, this thread went further than I expected it to, although I must admit, I've learned a few things...I think?

I guess let me simplify things to my specific situation. If you wanted to throw $4-5k at a car to be in for 750 miles a week while being somewhat practical, what do you think would offer the most bang for the buck without being insufferable? All are manual with good maintenance records.

1) 1999 BMW 528it, 190k 2) 2007 Mazda3 2.3 Touring, 150k 3) 2000 VW Jetta TDI, 238k 4) 2004 Toyota Matrix XR, 150k 5) 2005 Mazda6 3.0 Sport Wagon, 121k

You gotta drive them and see which one your azz fits.

I love me some Mazdas, but they are not gonna come close on the fuel economy.

238K is a little high for my comfort zone on the TDI.

I personally would not want the maintenance costs of the BMW, but its a completely different ride then the Matrix. Completely different feel. I don't believe anyone could like both.

Take 'em for a test drive.

In reply to SlickDizzy:

Like the old joke about how a man chooses between two woman when presented with education, experience, references etc. He chooses the one with the biggest boobs.

So given your list you choose the one that excites you the most. Your compensation is probably the government defined amount per mile, and that's factored off a new or new-ish car depreciation, insurance, shop maintenance, wear and tear etc. So if you're buying an older car from your list you are way way ahead with any of them.

For me from that list I'd be thinking the BMW, my list would probably read 08 Volvo C30, 05-10 Mustang GT, 986 or 987 S Boxster, E46 330i ZHP, C5 or C6 Vette, Volvo V70 etc. Different strokes for different folks.

No LS400?

I'm leaning toward the '07 3 Touring as, in my opinion, it has the best mixture of low maintenance cost, fuel efficiency and day-to-day livability.

Initially I was all for the 6 wagon but I was more than a bit surprised by the poor gas mileage. It's within 2-3 mpg of a Fox Mustang GT!

In reply to Adrian_Thompson:

What planet do you live on where ANY of those cars are under $6k!?! I'll take that $6k 987 or C6, please. My list is cars that are actually for sale within 100 miles of me...

I'd be looking at an Acura RSX or Civic of some sorts for that price range. I'm not a Honda fan but they are tough to beat with regards to MPG. At least the RSX is interesting to drive and look at and has a nice shifter.

In reply to amg_rx7:

Those are also two of the top five most stolen vehicles where I live, with most used examples all having salvage titles, and that's aside from the twice-as-high insurance premiums...Honda makes good cars, but it's just not going to happen until I have garaged parking at home again.

curtis73 wrote:

yupididit wrote: One time in my ecoboost fusion I was able to cruise at 60mph via cruise control for about 90 miles none stop. The car said was getting 45mpg and at one point 49mpg going down hill. But, I'm sure it was more like 38mpg. I wonder how the car computer calculates its mpgs.

Yup... it knows fuel pressure, delivery rate of the injectors, and the pulsewidth its telling the injectors to be open. The only one of those on-board MPG computers that I ever experienced that was close was in my e30, but it was only accurate because I had smaller diameter tires and didn't correct for it. The actual amount of time the injectors are open is rarely exactly what the computer tells it to do. It takes time for the injector to open and close before and after the signal from the computer. This effect is exaggerated at lower RPMs. It makes those computers pretty optimistic.

Injector response time is a known factor, and taken into account in the ECU programming. Even in our crude aftermarket stuff The computer knows exactly how much fuel is being injected.

Super interesting thread...

Not much to add other than my own experiences. My E36 once averaged 29mpg on a trip that averaged speeds higher than Im proud of and will hold 30mpg at a solid 80mph. All of that without cruise. With cruise at 75 I get a consistent 27mpg. My best explanation is that at higher speed the engine is closer to its peak torque and therefore is more efficient. Also, Ecomodders has a technique Im only somewhat familiar with that involves speeding up and coasting down to and from set speeds. Ive never actually tested it but it might explain why myself and others get better mileage while driving semi aggressively in traffic than at steady speed on the open highway.

SlickDizzy wrote: In reply to Adrian_Thompson: What planet do you live on where ANY of those cars are under $6k!?! I'll take that $6k 987 or C6, please. My list is cars that are actually for sale within 100 miles of me...

Opps, in all this talk of oil burners I'd forgotten that requirement. But my Caveat is that i said 'my list would be' not 'my list for you would be' Does that work as a get out of jail free card?

Seriously, I still stand by my statement of go for what floats your boat. From your list, I'd still pick the BMW, but that's because it's what floats my boat, not yours.

Seriously here's another one, much maligned, but personal experience says that as usual the internet pundits are way over blowing the supposed issues. For $6k you can get the nicest SVT Contour on the planet. A great mile eater, real fun to drive and if you're so inclined a great track day car. For your $6K you might even find a 3.0L conversion with an LSD

In reply to SlickDizzy:

Id choose that bmw e39, just replace the 100,000mile cooling system and enjoy

Have you done the math on any of these cars? How much more are you paying to not be in a Prius?

amg_rx7 wrote: I'd be looking at an Acura RSX or Civic of some sorts for that price range. I'm not a Honda fan but they are tough to beat with regards to MPG. At least the RSX is interesting to drive and look at and has a nice shifter.

I wouldn't say an RSX gets good mileage (of course, most cars on the OP's list do not). They have high ownership costs in other areas and are rust prone.

Ever spend more than an hour in a Prius? Seats are awful, awful. I'm going to be doing all of this driving while also being expected to get out of the car and work for 8 hours every day so I'm willing to sacrifice pure economy for something that doesn't suck to drive...any hybrids I have found in my price range are at failing battery mileage, so I am looking at used oil burners and reasonably efficient gassers. I'm aware a BMW 5-Series isn't a hypermiler but the entry price is low and running costs would be low for me as I am very familiar with BMWs, and at 6'3", being behind the wheel of one wouldn't kill me the way a Prius does. At 42.5 cents a mile I would be making money with any car on my list. The question is how much comfort I am willing to sacrifice to get that extra $50 in my pocket every week...

The seats are lame, but not painful in any way. I have a Gen1 that I take all long trips in. And I don't drive anywhere near 40k a year. At that kind of mileage, even a small difference in operating cost makes a huge difference in money in your pocket.

Just a data point and no I stopped reading everything posted :)

Aero is a big one. My '06 GT would get about 27 or so on the highway when driving. After I lowered it, the highway MPG actually jumped on average 1.5-2 mpg. So I was getting about 29 out of the car.

As far as cruise, I have always done better without using it. The main reason is that cruise just wantonly throws the pedal around to keep a speed. If you pay attention and use it sparingly plus you plan ahead speed down hills, lose speed going up you can increase your MPG. It is a HUGE PITA and makes you very tired just from the mentalness of it.

SVreX wrote:

Kenny_McCormic wrote: In reply to SVreX: How do you derive miles driven without having to assume a tire diameter?

How did you get from speedometer to tire diameter? I didn't say anything about tire diameter. Tire diameter can be presumed without a speedometer. Known tire diameter and gear ratio can give a very precise distance based on driven gear rotations. GPS is another way. There are probably others, but I am not an automotive engineer.

Most of your speedometer/odometer inaccuracy is coming from tire diameter inaccuracy. The computer is getting the miles part of its miles/gallon calculation from processing either the VSS signal into distance(most likely), or going by RPM and gearing, both using an assumed tire circumference. So however far off the tire is from the programmed number(or by extension, the speedometer/odometer) is how far off that mpg calculation will be, assuming the fuel volume number is dead on.

...Prius with an aftermarket seat

OHSCrifle wrote: ...Prius with an aftermarket seat

Life is too short to drive refrigerators.

Adrian_Thompson wrote:

OHSCrifle wrote: ...Prius with an aftermarket seat

Life is too short to drive refrigerators.

I disagree. Life is too short to piss money down the drain commuting in the wrong vehicle.

But really, life is too short to drive 40K miles a year just to get to work.

In reply to ProDarwin:

It's actually closer to 20k. I'm running the new job site on a bi-weekly basis, rotating with another guy, and this whole thing is only projected to last for a year. I'm not sure I want to stay with the company much longer than that anyway.

I'd get the Matrix XR or Mazda 3 and run it into the ground. They are both very comfortable and soak up the miles well.

ProDarwin wrote:

Adrian_Thompson wrote:

OHSCrifle wrote: ...Prius with an aftermarket seat

Life is too short to drive refrigerators.

I disagree. Life is too short to piss money down the drain commuting in the wrong vehicle.

This is my philosophy. I have commuted in a variety of different cars, when the commute is a pretty boring freeway/urban surface street grind (i.e., not twisty backroads) then you really don't benefit from doing it in a fun/sporty car. Rolling down the superslab or sitting in stop-and-go traffic in my 350Z was no more fun than doing the same is now in my Honda Fit, and maybe even less fun because the Fit rides better and is easier to see out of.

I'm not going to read 5 pages, so this might have been done. I also haven't done the math yet...40,000 miles divided by 40 mpg is 1000 gallons of fuel, right? For easy math, lets say gas is $4.00 a gallon, so that's $4,000 per year in gas. 20 mpg would be $8k, 30 would be $6. OK, I guess its worth the cake to buy the extra cost of a diesel...except diesel is currently 31 cents a liter more here, so I presume its a buck a gallon more down there...We also have to factor depreciation and maintenance costs into the deal, so German and diesel kinda bring the costs up...

And you have to drive a diesel.

I'd buy the best 30-35mpg $3k car I could find and drive it into the dirt, and if it blew up on the side of the road, I'd find the next one on craigslist and hitch a ride to it.

Adrian_Thompson wrote:

OHSCrifle wrote: ...Prius with an aftermarket seat

Life is too short to drive refrigerators.

On the other hand, life is too short to beat yourself up commuting in a hot rod.