I've got a 2005 Sonata with the 2.7L V6 and automatic transmission, I'm looking to up the combined mileage past 20 MPG (which is what I've worked out its mileage as being). A friend of mine who has worked on several cars of many makes told me to get new spark plugs, change the oil with Mobile 1 Synthetic, get a purolator oil filter, K&N Lifetime air filter, change the PCV Valve and check for vacuum leaks. Is there anything else I can or should do to the car?
Is there any way for me to lighten the interior of the car without replacing all the seats and removing the back seat? I'm a college student so I do need all the seats to be intact, otherwise I'd remove the back seats and weld the rear doors shut.

 

Change you driving style. Seriously, the driver can make the biggest difference in fuel economy. Easy on the gas, coast to stops, cruise control on the highway, don't speed, etc. That along with making sure the car is in good running order and the tires are properly inflated and aligned.

My 2006 Tucson has the exact same engine and I fuel economy numbers in the low to mid 20's. That's about 50/50 to 60/40 highway/city driving. My Tucson is heavier and less aerodynamic than your Sonata.

 

I drive like that already, but I do drive about 30-40 miles per day, 7 days a week.

I don't speed, always use cruise control, I never jack rabbit and only stop suddenly when those in front of me do. I go below the speed limit on local roads to make the coast to stop smaller. I want to know what I can do to it mechanically to increase fuel economy.

 

Not much other than making sure the engine is in good running order. Good plugs, claen air filter and MAF, etc

 

So all the stuff my friend told me to do is pretty much all I can do then?

 

Seriously? Maybe you need to get a different car.

 

I have an 06 Sonata 3.3L V6 and average 24mpg dirving 90% highways. Cruise control doesn't not necessarily help with mpg because the car will compensate for speed on hills. Coast and do not accelerate for hills (allow your speed to drop). Get a spoiler.

 

Will increased downforce result in increase in fuel efficiency for Sonatas?

 

No. A spoiler and increased downforce will not increase fuel efficiency.

That post has lots of bad advice. Cruise control does help with mileage. Granted, on hills, cruise control will accelerate harder than you normally would but allowing your speed to drop on hills is also bad advice. That's how accidents happen. Maintain your speed. Just learn to cancel on hills that cause the cruise to speed up too much and then resume the cruise when the terrain flattens out again.

 

i have the 08 sonata with the 3.3l engine. on trips longer than 3 hours the mpg reads over 30 mpg. filling up after the trip indicates 29.9.......mpg. the car was loaded with 3 adults and a grandbaby in the winter. hope this helps!