Gas milage


#1

I have a 97 rav4 2.0 4cl auto with od and I get 28mpg on hwy 70mph 2400rpm.

A carolla with the same gets 34-38mph.



Why, cannot see it turning less rpms.

this has always puzzled me


#2

[b]Tire size, vehicle weight, and the final gear ratio all effect fuel mileage.

Tester[/b]


#3

Weight and aerodynamics mean a lot when it comes to mpg.

Not to mention driver habits, tire pressures, trunk weight, passengers, clean or dirty (yes, that DOES make a difference too), etc.


#4

Wind resistance increases as the square of the velocity. Aerodynamics has a lot to do with reducing the wind resistance which is called drag. The shape of the vehicle can make a big difference. For example, the 1949 Nash with its “AirFlyte” design generated 113 pounds of drag at 60 mph. The 1949 Packard, which had a similar appearance, generated 171 pounds of drag at 60 mph. Less drag translates into better gasoline mileage. A leading engineer at Nash, Nils Erik Wahlberg, did extensive tests of shapes in a wind tunnel and this “Airflyte” design was a result of his tests. Another interesting result of Wahlberg’s wind tunnel research resulted in better heating of the cabin in the winter. The heaters used to be a box with a heater core that was placed under the dashboard and recirculated the air in the cabin. Wahlberg’s research uncovered the fact that the pressur inside the car was less than the outside pressure. Therefore, the cold air would creep into the cabin through any crack or crevice. Wahlberg’s solution was to induct air from the outside and heat it, thus pressurizing the cabin. The pressurized warm air would escape to the outside rther than the cold air infiltrating the cabin. Nash then introduced its “Weather Eye” fresh air heating system which was ultimately adopted by all manufacturers. Unfortunately, the public didn’t like the shape of the Nash automobiles, and so a couple of years later, Nash went to a more conventional styling. The gasoline mileage dropped as a result.


#5

Maybe because there is no direct relationship between RPM and mileage.


#6

The RAV4 also weighs probably 1000lbs more than a Corolla, and has 4 wheel drive, which the Corolla doesn’t have. It’s comparing apples to bricks.


#7

Even if both engines are operating at the same RPM and speed, the engine in the RAV4 will be operating under higher load, which will therefore require more fuel.

You can check this by hooking up a vacuum gage to full manifold vacuum on each car; at the same driving conditions the RAV4 will be operating at a lower vacuum, indicating the engine is ingesting more air. The more air the engine ingests the more fuel is required.

Strangely enough, the RAV4 will be operating at a higher volumetric efficiency than the Corolla , even though the Corolla is burning less fuel :slight_smile:


#8

thank you loafer that makes sense