Fuel efficiency now & then

Some 30 years ago I had a Mazda wagon that got 48 mpg. Now I have a Subaru Forester that gets 24 mpg. I believe one major difference is the catalytic converter. And I believe the catalytic converter had something to do with unleaded gas (and I’m sure you will correct me if I’m wrong…).

Now I know there are great benefits to having removed the lead from gas, but now I’m burning twice as much gas - how is this really better? Even the “Smart Car” doesn’t get 48 mpg - and it’s really small.

I’ve asked this question of many people and no one, so far, has been able to give me an answer.

Thanks, Susan McDaniel

Carrboro, NC

It’s not the catalytic converter, that does not affect mpgs. Your Forester is much heavier and safer than the Mazda, and it has awd.

Also, I question your ‘48 mpg’ number. The 1984 Mazda GLC wagon with a 1.5 l manual 5 sp has EPA rating for the highway of 27 mpgs. Quite a difference from 48.

The difference between now and then is that your Subaru probably weighs twice what your Mazda did, and it has two extra differentials.

Also, I guarantee your Forester is capable of more than 24 MPG. Your driving style may have changed as well.

As for the Smart car, some of the European versions CAN get 48 mpg. The US version doesn’t have the right engine or gearing for it.

Oh yeah, that’s another thing: gearing. The gear ratios (and wheel size) between the engine and the road are what determine how fast the engine has to run to maintain a certain speed. Having a “tall” top gear is how the Corvette manages to have such good highway fuel economy.

And on the subject of wheels: The wheels on your Forester are larger, which helps the ratio between them and the engine, actually. But that also means they’re heavier. It takes more energy to get them moving. That hurts fuel economy. They’re also wider, with larger contact patches and more sidewall to flex when they roll. That also wastes energy that isn’t wasted on your Mazda. Almost all cars these days are like that. You would probably have a hell of a time finding tires these days to fit your old Mazda.

Oh, and then there’s power. Modern engines are actually more efficient than anything you could get in the 70s. They just make a LOT more power. Your Forester is probably 3 times as powerful as your Mazda was. Power sells. Given a choice between a car that gets 1 mpg better fuel economy and one that has 10 percent more power, most people will choose the one with more power. Now keep doing that for 30 years, and you end up with 150 horsepower economy cars, and no improvement in fuel economy in the last 30 years. (And the near-complete disappearance of extremely-fuel-efficient cars.)

That, too. I don’t doubt there was SOME mazda, SOMEWHERE that was capable of 48 mpg, but not under the same driving conditions as the Forester getting 24.

Checking fuel mileage with one tankful can indicate wrong results. To get a reliable number you must refuel at the same pump on the same parking pad and to the same shutoff level. Even with all of that you can “pack” the tank on either the first or second fill to bias the resulting fuel mileage calculation. It is very easy to do and the differences can be remarkable. Several fills with the same conditions can average out the errors.

With all of that done wisely, the pump may be out of calibration. I have personally seen that with experience filling 5 gallon gas cans on several occasions at the same pump.

I agree with the above. Unfortunately, you may be suffering from the old adage that I do as well.

“The older I am, the better I was.” and everything else too. Memory does that to us.

Considering most 4cyl engines rival those older V8s in terms of horse power(torque is a whole nother ball game though). I remember my Chevelle being rated for just under 200hp, it isn’t unheard of for a modern 4cyl to have that much power. My Chevelle got 13~15mpg, most 4cyl engines with that much hp will get better fuel economy than that.

Also, I’d mention that the “Smart Cars” we get here are really poorly engineered little things. For one, in Europe they come with much more efficient little turbodiesel engines, while the gas engine was just sort of an afterthought so they could sell them in the US. Also they’re not really that small in any of the dimensions that improve the car’s aerodynamic profile-- they’re still tall and have big flat rear ends. They’re great for places where parking is an issue, but they’re actually not the best for gas mileage.

Every time I see a “Dumb Car”, I think of a Yugo. And may they come to the same end.

1980’s Honda CRX HF got over 41 MPG. But, it had a 1.2l engine and weighed 1,300 lbs. Add all of today’s safety stuff and you’re over 3,000 pounds. Tighter emissions also change the picture.


At least Yugos were cheap. I wonder if this is one of those instances where charging more improves people’s perception of the product.

Susan, as others point out, you are comparing apples and oranges. Your old Mazda also did not nearly get the mileage on average that you remember. We all remember the good stuff.

If you want to go back to the level of performance and comfort of the Mazda, you need a Toyota Yaris, a Hyundai Accent or similar vehicle. Even those are a lot more powerful than your Mazda was.

The wife of a friend of mine had a Mazda GLC in 1984, and, although frugal, I do not recall it getting anywhere near 48 MPG.

The catalytic converter has little to do with efficiency. Early models did not perform well, but that was in 1976.

The GLC weighed 1790 pounds. The Forester weighs 3460 pounds. This should answer your question.

My first car was a Sunbeam Imp, smaller and lighter than my second car a VW Beetle. It got 40-45 mpg, the Beetle got 34-38. Today I drive a new Beetle and get 45-60 mpg. It is a bigger heavier car than that either of those 1960’s cars.

My Forester gets 24 mpg too. Check your PCV valve. If it’s crapped up, a new one will give you noticeable improvement. That’s about it, unless your running with some really bad plugs and messed up injectors. Your Forester is NOT twice as heavy as the Mazda. But Foresters are absolute champions in their size class for catching wind. Compare your front profile to a Subaru Legacy Wagon and you will have most of the answer you are looking for. Wife has the 2004 Forester at 24 mpg. I have the 2000 Legacy Wagon at 35 mpg. Everything else more or less equal. Look at it this way, in addition to super safe and amazing AWD, your ride will last twice as long and cost half as much to maintain as anything else in any price range - today, 30 years ago or any year in between. Gospel truth.

The converter is not the reason behind decreased mileage but the OP does have a valid point and I wouldn’t completely discount the 48 MPG claim. The son of a Subaru dealer I used to work for owned a '77 Subaru 2 DR FE model (1.6, 5 speed) and that car would routinely get 45 MPG on road trips.

Consider the following.
A 1985 Subaru with a 1.8 EEC controlled carburetor and 5 speed manual will routinely get 38-40 MPG and can even get a bit better at times.
A 1986 Subaru with a 1.8 OHC (same engine only with overhead cam), fuel injection, and what is essentially the same car (size, weight, but only more aerodynamic) would get about 30 if one was lucky.

And this was verified more than once with a fuel mileage tester because in the case of the EEC carbureted cars there were complaints about “only getting 30 something MPG” or what have you.

One in particular I remember very well because the owner of the car was an oil field lease security company who used it to patrol oil leases.
They were complaining over “only getting 38 MPG” and it took a number of tests to prove to them that they were getting 41 steady as a clock.

It was 1.3 liters, and 1800 pounds, but you’ve got the general idea right.

Oh, and I don’t think new emission controls have anything to do with it…most of the measures taken to reduce them in the last 20 years either have no effect on or actually help fuel economy.

Rather than killing fuel efficiency, I think the catalytic converters actually gave emmission complient vehicles back the ability to get good gas mileage by taking away the need for lean fuel mixtures and retarded spark timing.
The EPA never mandated catalytic converters. If a car could meet emmision standards without them, they didn’t need one. The Honda super lean CVCC engine was one of the last non-catalytic holdouts. The EPA mandated unleaded gas in order to make catalytic converters possible.

Aerodynamically, a Smart Car is like a billboard going down the road sideways. You might as well just hook a parachute to the trailer hitch.
If you want a really clean car that can get 60+ mpg on the highway, take a look at the first generation Honda Insight with its covered wheel wells and boat tail rear end. That’s what cars are going to have to look like if we really get serious about mpg.

Yes, the combination of catalytic converters with fuel injection and electronic engine management has resulted in engines today that are far more efficient that the ‘old days’. What’s messed up fuel milage is the huge weight increases (safety) and performance increases people now demand. 0-60 mph in under 10 seconds used to be for ‘performance’ cars. Now just about every ‘economy’ car does that.