A car’s weight has a dramatic effect on its performance, ride, handling, and fuel economy. Figuring out how much a car weighs should be simple, but the weights listed in brochures, road tests, and other sources can be contradictory and confusing. A vehicle’s specifications may list shipping weight, manufacturer’s curb weight, and gross vehicle weight ratings, all of which are quite different. To sort out this confusion, let’s look at what each of these terms means.
Dry weight is a vehicle’s unladen weight with a completely empty fuel tank and no engine oil, coolant, or other fluids. As you can probably guess, dry weight is consequently much less than the car’s actual, on-the-road weight. One U.S. gallon (which equals a bit under 3.8 liters, for our metric readers) of plain water weighs about 8.4 lb (3.8 kg) while a U.S. gallon of gasoline something on the order of 6.5 lb (3.0 kg). Consequently, just adding fluids and filling the gas tank can add 150 lb (68 kg) or more to a car’s dry weight.
Since passenger cars are generally (though not always) shipped with oil, coolant, and other vital fluids, dry weight is not often quoted for complete automobiles, although the term is sometimes used, albeit not always correctly, as a synonym for shipping weight. However, the quoted weights of automotive engines are almost always dry weights (and may or may not include accessories or the weight of the flywheel or flex plate).
Unless you pick up your new car directly from the factory, the manufacturer has to ship it to dealers by sea, rail, or truck. Because freight charges are usually based on weight, automakers frequently publish a standardized shipping weight for each model they sell. If a model is available with a choice of “standard” engines — e.g., a mid-1960s Chevrolet with either a six or a V8 — the manufacturer will sometimes list separate figures for each engine or quote the additional weight added by the larger engine and its associated equipment.
Shipping weight usually reflects a “stripped” model with a standard engine and no optional equipment. It typically includes engine and transmission oil, engine coolant (if the engine is water-cooled), and at least a modicum of fuel — enough to start the engine and drive the car off the truck or transport pallet. In some eras, however, filling the radiator and fuel tank were left to the dealer. As a result, it’s not easy to be sure whether quoted shipping weight included those fluids without detailed knowledge of a particular automaker’s standard procedures in that period.
Like dry weight, shipping weight is usually substantially less than the car’s actual, ready-to-drive weight. Aside from the weight of fuel, optional equipment or engines can add a great deal to the car’s total mass. For example, a 1965 Ford Mustang with the optional 289 cu. in. (4,728 cc) V8, automatic transmission, power steering, radio, and power brakes weighed at least 400 lb (181 kg) more than a stripped six-cylinder model. Adding to the disparity, a lot of equipment that we’ve come to expect on modern cars — trivialities such as heaters, turn signals, and even spare tires 00 were at least nominally optional in earlier eras. It’s unlikely that many cars were built without those features except perhaps by special order for fleet buyers, but since those options were not technically standard equipment, their weight was not reflected in the published shipping weights.
Shipping weight is best understood as a particular model’s practical minimum weight in stock form. For that reason, some racing organizations have used factory shipping weights to determine eligibility for different racing classes. (Depending on the rules of the specific class, a minimum weight figure may also be imposed to limit competitors’ ability to further lighten the car by removing trim and standard equipment or substituting lightweight components.)
A vehicle’s curb weight (or kerb weight, for our British readers) is its weight in unladen, ready-to-drive condition — still with no driver, passengers, or cargo, but with all necessary fluids, including fuel. In the United States, curb weight is typically measured with a full tank of fuel. For cars sold in Europe, automakers today frequently specify DIN curb weight, which is with the fuel tank (or tanks) 90% full.
European Union type approval rules also require manufacturers to specify a vehicle’s weight with the fuel tank(s) 90% full plus an additional 165.3 lb (75 kg) to account for the weight of the driver and a small amount of cargo. The total is often called E.U. curb weight or licensing mass.
The manufacturer’s curb weight is the curb weight listed in the automaker’s official specifications. Depending on the market and the manufacturer, this may be the E.U. licensing mass or the car’s weight with either a partial or full tank of fuel; there’s often no way to be sure just by looking at the spec sheet.
As with shipping weights, these figures generally do not include optional engines or equipment. Some manufacturers specify an average figure or list separate curb weights for each model and powertrain combination. (The E.U. requires automakers to calculate the mass of optional equipment to ensure that the options don’t push the vehicle over its maximum safe load limit, but the mass of that equipment isn’t necessarily published.) Most automakers simply list the weight of a stripped model, although automakers occasionally publish lists specifying the additional weight of major options, such as automatic transmission or air conditioning.
Some independent auto testers actually weigh each of the vehicles they test and list the vehicle’s actual curb weight in the test results. These figures are typically higher than the manufacturer’s figures because they reflect the optional equipment the car actually possesses rather than the standardized figure.
Some magazines and testers also list the actual test weight of their subjects, which is the curb weight plus the weight of the driver and any test equipment. In the 1950s and 1960s, in particular, test weights were often substantially higher than curb weights, reflecting the bulk of period test equipment and, in some cases, the necessity of carrying a passenger to operate it.
Gross Weight and Gross Vehicle Weight Rating (GVWR)
A car’s gross weight is its curb weight plus the weight of its driver, passengers, and cargo. A car’s gross vehicle weight rating (abbreviated GVWR, but often confusingly listed as just gross weight) is the manufacturer’s recommended maximum loaded weight. The vehicle’s maximum load is the GVWR minus the curb weight. For example, a vehicle with a gross vehicle weight rating of 5,500 lb (2,495 kg) and a curb weight of 3,800 lb (1,724 kg) has a maximum load of 1,700 lb (771 kg). Naturally, a vehicle’s actual gross weight changes depending on how many passengers and how much cargo it’s carrying, but its gross weight rating does not.
Gross weight ratings usually assume the standard suspension and standard tires inflated to the recommended pressure. Manufacturers occasionally specify different gross weight ratings for different combinations of suspension and tires, although that’s more common for trucks than for passenger cars.
In many nations, including the U.S., gross weight rating determines what roads a vehicle is permitted to use, what type of driver’s license and insurance are necessary to operate it, and the emissions and fuel economy standards it must meet.
APPLES TO ORANGES
At Ate Up With Motor, one of our goals is to put each of the cars we discuss in context, both with other cars of its time and with modern vehicles. Unless otherwise noted, when we refer to a car’s weight, we mean its actual curb weight with a full tank of fuel, not its shipping weight or gross weight rating.
As you can see from the above discussion, estimating the actual weight of a vehicle with options and a full tank of fuel can be tricky unless you’re in a position to take the vehicle and put it on a scale. A lot of sources simply quote the manufacturer’s or other published figures without specifying (or perhaps even considering) whether those figures are curb weights or shipping weights, whether they reflect the weight of optional equipment and a full tank of fuel, and so on. And don’t get us started on the quaint habit of older British publications of rounding all masses to fractions of a hundredweight! (For those not familiar with pre-metric Imperial measurements, a British hundredweight, abbreviated cwt, was equal to 8 stone or 112 lb, which happened to be roughly equivalent to 50 kg or 1/20th of a metric ton. It was therefore a handy way of approximating Imperial-metric conversions in the era before pocket calculators.)
As a result, the weights we cite are usually approximate. We would much rather tell you, for instance, that a car weighed “about 2,400 lb” than claim it weighed exactly 2,408 lb at the curb; the latter figure might be true for one specific car with one specific combination of equipment and amount of fuel, but won’t necessarily be accurate for a different example equipped slightly differently. If you compare our estimates with the specifications of other cars (or figures listed in different sources), be sure to note whether the numbers to which you’re comparing them are referring to curb weight or shipping weight — as you can see, it can make an enormous difference!
6 CommentsAdd a Comment
Great info. So cars in the 60s (Supercars as you call them on the site) not only had misleading horsepower figures but misleading weight as well? Testing equipment (even at racetracks and etc) would also have been much less accurate than modern equipment.
Suddenly it doesn’t seem as weird to read that modern economy cars are just as fast or faster than the Supercars of old. I will have to remember all this when reading figures on my old favorites.
Well, it’s not really a question of testing [i]accuracy[/i]. If you took your car to the track and entered it in a competitive event, the tech inspectors would weigh it with a reasonable degree of accuracy; the published power-to-weight ratio was used to determine class [i]eligibility[/i], rather than qualification. Mostly, it’s a matter of ambiguity. It’s not that the weights are necessarily wrong (although sometimes they were…[i]Motor Trend[/i] went through a period in the early seventies when a lot of their specifications were just wrong, a result of somebody doing the editorial mark-up who didn’t know what they were doing) — it’s that you don’t know what weight they’re quoting. It’s often very unclear whether they’re relying on manufacturer figures or whether they’ve actually put the car on a scale. The only publications in the sixties that were consistently good about that were [i]Car Life[/i] and [i]Road & Track[/i], although even there, there are some moments where you wonder. If it was just a few pounds, it wouldn’t be significant, but the difference between the factory shipping weight of, say, a Ford Fairlane V8 (with a 289) and the actual curb weight of a Fairlane GTA with a 390 and C6, can be hundreds of pounds.
Gross hp is NOT misleading. All that is important to anyobody is the RELATIVITY of the numbers. No-one outside of an engineer or a scientist can actually picture what say 210hp is. But everybody can understand that 210hp is a bit more than 180 and a bit less than 250. As long as discussions are framed in the same units (gross or net) all is well. Same with torque.
Weight is a more comprehensible issue and after reading the words above I believe that for general comparison purposes the use of curb weight is best, with actual weight used for road tests.
If gross horsepower were simply a matter of units, it wouldn’t make a difference; in that sense, it doesn’t matter if you’re talking about hp, PS, or KW. If everyone used exactly the same methodology, it also wouldn’t matter very much. However, as outlined in the article on gross vs. net horsepower, it wasn’t nearly that simple. A lot of gross ratings were, shall we say, rather generous, while others were deliberately conservative. Gross ratings also didn’t reflect things like add-on emissions controls (thermal reactors and the like). There were many cases where, for example, an engine with a gross rating of 290 hp might actually be more powerful than one with a gross rating of 325 hp (e.g., the first-generation Camaro Z/28 and SS 396) or two engines with identical or nearly identical gross ratings actually had substantially different outputs (e.g., the Pontiac Ram Air engines). So, the differences were not nearly as cut and dried as the differences between a 180 lb man and a 225 lb man.
Many of the articles you read online at any blog or car site like to drag on about how heavy cars have become due to safety requirement and such. Obviously cars were lighter without airbags and heavy bumper and high beltlines (a styling/safety trend I really hate) but this narrows the reality gap just a bit.
If I would estimate in my mind an old mid-size Chevy weighed 2800lbs (very loose estimate) but if my estimate has been skewed a bit due to bad figures and it was really 3000, that changes the picture a bit in my mind. My current car is about 3300 lbs, and it’s horsepower to weight ratio is suddenly tons better in comparison to say, a Nova with a 396 in it when the engine is less powerful than the numbers said, AND it was heavier too. (In this case assuming the stated weights were all for the I-6 base model Nova.)
My stepdad was big on classic cars, mostly Novas as it were haha and I have ridden in tons of classics in my life (Oldest I ever owned was a ’78 Nova, no classic there) but they were all modified. I can’t say I have any experience with stock Supercars.
I think that the current high-beltline look is a fashion trend, more than anything to do with safety, but I, too, will be glad when it runs its course. I don’t find it reassuring to feel like I’m driving from a bunker.
If by midsize Chevy you mean a mid-sixties A-body Chevelle/Malibu, it was a good deal more than 2,800 pounds. Even a stripper six-cylinder Chevelle 300 with three-on-the-tree was a little over 3,000, and the actual curb weight of a typically equipped ’64 Chevelle with a small-block V8 was between 3,300 and 3,400 pounds. The ’65-’67 models were a little bulkier and heavier, and the big-block engine added a lot of extra mass: an SS396 was 3,650-3,800 lb, depending on equipment. (Just the dry weight alone of the 396 was 150 lb more than a 283/327 small-block, and that’s not counting other drivetrain components.)