I have a hobby of trying to max out the gas mileage in my cars and the latest Ginnie Pig is my 97 960.
Well back in Nov I made a MPG run with my 97 Volvo 960. It was my usual base line route Pittsburgh to Erie and back I always take after making any kind of mpg mods to the car. Speed is held to 65 mph and tires are inflated to 40 psi.
My base mileage on this run is an even 28.0 mpg which was run in July.
Well to the meat of the facts. At the front I enclosed the openings between the bottom of the fenders to the edges of plastic splash pan with Aluminum. This is an open area under the battery and the corresponding passenger side.
Heading towards the rear I placed a steel air deflector plate attached to the bottom of the suspension cross member. This was done to keep the air from being pulled up into the IRS frame work while it is flowing under the car. From there I ran an aluminum plate all the way back to bottom of the rear bumper. I did leave the rear muffler exposed due to the heat.
All in all I got an astounding 3.0 mpg increase with this mod. This has been probably the best mpg increase from all the mods I have made. When I bought the car Feb 05 I got 25.3 mpg on the highway and today 31.0 mpg. 5.7 mpg or 18.4% increase is nothing to complain about. Plus I figure this spring I'll spend a little time cleaning up the rest of the under carriage. That should be worth another 1/2 to 1 mpg.
For those that are interested in all the mods.
This RWD car weighs in at around 3500 lbs and has a Cd of .36
I started with an Auto-Rx engine cleaning. A clean engine is an efficient engine. That helped me get the car to 26.3 mpg, Then I swapped out all the fluids for synthetic and I saw 27.4 mpg. I then increased the tire pressure from 36 psi (factory) to 40 psi and saw 28 mpg. With the addition of the belly pan mods I now get 31 mpg.
My Scan Gauge matched the gas pump when I filled up with 8.238 gallons of gas for 255.7 miles.
At Christmas I drove down to Fl. to visit family a 1180 mile trip, even with winter gas, driving through the mountains of WVa. and the sub freezing temperatures I still got a respectable 29.3 mpg highway. At my fill up on I - 26 near the I-26/ I-95 split to Fort Myers Fl. I averaged 31.3 mpg.
On the way home I averaged 30.5 mpg the first tank filling up close to the I-95/I-26 split. From there I got 29.1 mpg on the way back through the mountains to Morgantown WVa. where I filled up again. Averaging 30.05 mpg in the winter isn't half bad in a 960