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Average increase in mileage

I was wondering on average for cars, what kind of increased miles per gallon can you get from driving freeway over city driving? I have seen as much as 12-15 miles difference in newer cars, but what about cars and such that are 8+ years old.

Too many variables. Some vehicles deliver significantly higher mileage on the highway vs city, and others do not.

I once had an '85 Ford Crown Vic that delivered a steady 17.5 mpg regardless of how or where it was driven.

With a hybrid…you’d actually see a decrease…

But for conventional cars…the MOST I’ve ever seen is close to 10mpg…As little as 3mpg…As mcparadise said…too many variables.

Lots of variables, from one make and model of car to another, depending on its transmission ratios, axle gearing, torque curves, aerodynamics, tires, etc.

On my '71 Charger, my usual 13 mpg in city driving could shoot all the way up to a spectacular 17 mpg on a long highway drive. By comparison, my '11 Outback, which is more powerful than the Charger was, gets a consistent 22-23 mpg in local driving, and I can eke out 28 mpg on the highway.

I think that Mike’s statement is right on the money. Depending on the make, model, and how the car is driven, the difference between city and highway mileage can be anywhere from ~3 mpg to ~10 mpg.

I have a 2006 honda CRV. I live were it is not real cold in the winter. I keep very close records on every oz. of gas I use. I live in a small city of 120,000 ,in the city in winter I avg. 22 MPG, summer in city avg. 25 MPG. Highway with no head or tail wind Avg. 35 MPG. summer or winter. Years ago I lived in a small place of 8000 , very cold in winter down to minus 40 many times. I owned a 72 plymouth with 360 motor, in town in winter avg. 7 mpg. summer about 12, highway 19 mpg. Honda Bill.

The widest swing I’ve personally been involved on old cars with was on several of my old muscle cars; primarily the Roadrunner and Superbee. (Both with 383 Magnums and 4-speeds)

On a light footed 65 MPH highway cruise I could eke out about 17 MPG at best.
Driving easy in town would get about 8-9 and “normal” driving about 5-6.
I have no idea what the MPG would be with the hammer down most of the time. A little hammering always caused the gas gauge to drop noticeably.

With my newer Lincoln Marks I generally get 27-28.5 and sometimes near 30 on the road and a consistent 18-19 in city driving.

It seems that with every gas crisis, the gap between city and highway mileage grows, when gas is cheap, the numbers are closer. For example, I had a 79 Dodge Colt, rated 28/37. Later I had a 90 Dodge Colt rated 29/36. Gas was relatively cheaper in the 90’s.

My wife has a 97 Accord, rated 25/30, the new Accord 24/34.

It seems that during periods of cheap gas, the final drive ratios are lower to give more apparent power, this helps city but hurts highway mileage. When gas is at a premium, the manufacturers use higher final drive ratios to boost that highway mileage, at the expense of city mileage. They only advertise the highway mileage.

My '96 ES300 would do 20 mpg in town, 28 mpg on the freeway. My '83 VW GTI would do 25 mpg, regardless (very short gearing).

Who’s driving the car can make a big difference in city driving. People who insist on accelerating towards each and every red light will get awful gas mileage in town.
People who drive as if the car’s brakes don’t work, anticipating stops and timing their driving to hit lights green if at all possible can actually beat the highway gas mileage in city driving.

Driving habits and speed traveled will make a lot of difference in how much the city/highway mileage varies. My '97 Ford Escort gets about 32-34 mpg in mixed local driving, on the highway it’s not uncommon to get 40-42 mpg and I have got as high as 48-49 mpg on the highway, but this was driving with the c/c set at 55 mph and not using the a/c.

I think I’d just look at the city vs. highway mileage posted by the EPA and go with that.

Acceleration of mass, aerodynamic resistance and rotational friction are the main things that destroy fuel mileage…