What did improve the fuel economy for you?

[Oliva77]

I was going to start a new thread because my experience with fuel economy is completely different. During the winter of 2005-6 I was driving 200mi+ RT to Vermont on I 89 which has sharper grades and curves than you might expect for an interstate. These trips were 95% highway. So I decided to experiment with improving my auto non turbo 98 V70's fuel economy. Same gas every time- Irving 87 octane.

First- cruise control at 70. Total failure- 2d worst result at 19mpg. The transmission downshifted on every grade- shooting the revs up- and braked downhill instead of coasting as I would. There are several reasons not to use cruise, this is one.

Second- having discarded cruise, I tried to keep the car at 2500rpm (62mph/100kmh on the flat) with my foot. 21, and I was averaging 23.

Third- 55mph using my foot. 20, and holy God that was a long trip. But it was nothing compared to…

Fourth and final- I talked to a guy from way the hell up north (never used interstate) who got 40mpg in his Escort by never going over 50, so- 2000rpm in top is 50 and I tried it sans cruise control. Head south from Lebanon and 2000rpm becomes 40 mph over the course of 500'. I was a hazard to my self, to other drivers, and I got a personal worst fuel economy at 18mpg.

I decided that momentum gained going down helped with going up hill.

The best mileage my V70 ever gave me was a trip to Burlington: 80-90 both ways. 25.7 pre ethanol.

10% was ethanol was introduced in my county early on. Accordingly I lost 10% of my mileage. Which I regained when I discovered the next county still had straight gas.

Now, several years and not many miles later, I frequently drive down to the Boston area, and the aggressive driving I learned in college has come to fore. And I'm getting better mileage- up to 24.5 from 22 at best. This is not sustained high speeds- there is too much traffic- but bursts of acceleration zipping in and out in the 128 style. I like to cruise at 90, but I'm not bothered if that creeps up.

Momentum- has to be. Higher rpms should equal more gas used, rolling resistance can't add much, what else?

[KEWROCK]

My V70 turbo All wheel drive averaged 23.5 Highway with no traffic averaging 70+mph. I consistantly landed on that average on my trips to Connecticut and Rhode Island from NY. I never really notice a difference during ethonol season either. The dash computer is amazingly accurate too. I tested it by filling up as much as the car would take, reset the trip odometer, then burning off the tank of gas. Fill up again, and divide the miles on the trip odometer by the gallons the car took. I consistantly get 18mpg driving around Queens and Brooklyn. I have a heavy foot at stop signs and lights, and tend to let the car idle alot.

My Jeep Wrangler only gets 12mpg combo city/hiway. That sucks!! I'm having a hard time jusifying driving it.

[shiloh51933]

I noticed improvement in gas mileage doing all the basic tune up parts/maintenance/service like spark plugs, cap/rotor, oil/filter change w/mobil1 5w30, proper tire pressure, pcv system service but the biggest gain that I noticed was from modding the air box stat and the throttle body plate from the 960. Not only did it improve throttle response, it improved our mpg's. I'm sure servicing the pcv system would have made a big difference if our pcv system was clogged up badly but ours wasn't too bad for a 100,000 miles on the odometer.

[abscate]

Biggest jump for me was

Positive - both O2 sensor replacement (BOSCH) took my highway mileage from 24 mph to 29 mpg

Negative - fixing my AC means now I use it on sweltering days...at 90F+ it took my same highway mileage from 29 back to 26 mpg at 70 mph. Of course, where I am, AC is only a 3 month thing, so Im not complaining.

[nedro018]

OP,

i just read thru this whole thread and sounds like you need to:

- bite bullet and replace (at least) the front O2 sensor.
- try different gas vendors and octanes.
- how are your tires? and alignment? alignment is huge.

i was getting 19-20 in town, like you. bought new front O2, modified air box for cold air (like you), vovlo plugs, new air cleaner, new tires and ran 2 psi high (needed them anyway), got alignment (and i knew it was out). now i get 22 mpg in town with ethanol, 24-25 with straight gas. i also hypermile like rspi does...i coast whenever i can. i give alot of space to erratic drivers in front of me and i spot a red light a mile away.

there's something else to consider with suck ass mpg's that the volvo's tend to get compared to the newer cars: INSURANCE costs. liability with my 95 850 NA costs (me) $20/mo. full coverage on your avg 2009-ish car is $50-55/mo. more for newer cars. keep this in mind.

[qoyi]

I got a V70, 2,5 TDI 103kW, I still rarely get better than 21mpg, even if I go 80kmph on cruise control, for a long way like 300kms. Tires are new, A/C does not work so it's off all the time. Air filter is new. Will try to change fuel filter (maybe it's already changed, I don't remember. I still think that going only 600kms for a full tank is a bit low. With my last V70 I did always over 1000kms even when I was speeding (180kmph).

[kcodyjr]

Of all the odd things, swapping the TCM from a 96 855 NA into my 97 854 GLT was good for 2-3mpg across the board.

The main thing is that it locks up the torque converter at 45 rather than 52 (is it 52?). This does allow for minor lugging.

In addition to the mileage improvement, I got a real noticeable difference between Sport and Econ modes, where before it wasn't really worth flipping the switch.

[oragex]

There are both mechanical/sensor issues, and maintenance items involved.

In order, what helped the most
- cleaning injectors in ultrasonic bath
- removing the intake air thermostat flap to the air filter box
- using proper 91 gas. Many Gas stations mix 87 fuel into the 91 reservoir, when filling the tanks. Widespread practice

[abscate]

Biggest improvement....switching from P80 manual (27 mpg) to a P2 manual (32 mpg)

[sleddriver]

An old thread, but still useful. One thing missing from the checklist is Stage 0 on all vacuum lines, rubber elbows, EVAP hoses AND the big brake booster vacuum line. LOTS of rubber hoses on turbo cars to leak! This means unmetered air leaks. Bad juju.

If either rigid plastic line from the oil separator box cracks inside the foam tube, you will now have a major vacuum leak right at the turbo inlet. There's not a worse place, save for the vacuum tree. Those little tree nipples can get rock hard and leak. The tree base o-ring can leak after time. Those two B/W check valves in turbo cars can fail over time. Build yourself a simple smoker and do the engine, intake, gas tank....all of it. Also driving around with a fuel pressure gauge duct-taped to the windshield will be very educational.