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Improve Gas Mileage V8 XC90

13K views 8 replies 7 participants last post by  4strokesmoke  
#1 ·
Ok ok ok, don't kill me if this has been posted before, because I've been searching and haven't found anything.

I have a 2007 Volvo XC90, and it is one of the best cars I've ever had. Really, it's only failing is the horrible gas mileage. I've been averaging 13-14 mph because I mainly do city driving. It is stage 0 as I've been good about doing preventative maintenance such as plugs, engine air filter, tire pressure, etc.

For the 2011 model year XC90 V8, the posted fuel economy is slightly better than previous models. I want to know why and if it is worth it to alter my vehicle to get the better gas mileage. My guess is it is different programming on the ECU combined with a couple of things like different injectors or something along those lines.

Does anybody know? I called IPD, and they didn't know. I've found chip tuning companies that can get a little more horsepower and torque out of the engine with a corresponding improvement in gas mileage (if driven softly), but these chips cost around $1000. If it was as simple as the stock programming being better on the 2011 XC90 (and it was backwards compatible with mine), I'd just get an ECU from one at the junk yard or on ebay and make the swap.

Thoughts or suggestions are greatly appreciated.
 
#2 ·
Best way to increase MPG? Get it out on the highway. I just was on a 6 hour round trip. Almost 25 MPG.

City driving sucks for MPG in the 90. I get about 15 in town.
 
#3 ·
Think of it this way, though: if you spent $1000 to increase your overall mpg from 14 to 15, it would take you something like 70,000 miles of driving to just break even in that investment. For now, focus on your driving style and make it a game to improve your mpg, for free.
 
#4 ·
For the most part, improving gas mileage means overcoming friction, road friction that is.

There are all sorts of things you can do to improve mpg. But here are 3 simple ones:

- make sure your tires are properly inflated. As a rule I go +2lbs higher than stated on the door pillar label.

- have a proper alignment. Any competent tire shop can do this. No need to go to the stealership: too much toe-in will dramatically increase tire shoulder wear and cause unnecessary drag. Don't just drop off your car and say "alignment please". Get involved, learn what it takes to get an optimum alignment. I specify: not zero, but slightly negative (pointed in), around 0.02 to 0.04, same front and rear. This is hard to do for an inexperienced tech. Camber value to be in center and symmetrical. That's it! Put it on the work order. Have store manager sign and agree. If the shop doesn't meet it with BEFORE and AFTER measurements print out as proof, send it back to the rack, or don't pay and move on to a shop that will.

- drive conservatively: use cruise control, whenever possible.

Doing just these 3 things, I average 24 to 25 mpg on the highway, only 14 mpg city with my 2009 V8.

No need to spend $1,000+.
 
#6 ·
As some said already: plan your driving. The consumption is manageable as long as the gearbox uses lock-up, but in heavy start-stop traffic you'll be using little of it. First gear has none and between shifts it's released and takes a moment to settle back in, if at all - depends on the adaption of the gearbox and your current driving pattern. Low revs is not necessarily the way to go, but using lock-up is. As an example, having the same model year and gearbox as you: Mine shifts into third at about 25 km/h and doesn't engage slipping lock-up until 30-35 km/h somewhere. I get better mileage going 75-80 km/h rather than 70 km/h as in the former case I get full lock-up and at 70, despite lower revs, only slipping lock-up at best.

What kind of city driving do you do by the way? If you do a lot of driving at speeds below 50 km/h then there's not a lot to do really. I get okay mileage in fifth at 55-60 km/h, if I'm able to keep a steady pace.
 
#7 ·
Pump up the tires to around 40psi that should have some affect on it as well.
 
#8 ·
Thanks for suggestions!

Thanks everyone for your thoughts and suggestions. I'll try pumping my tires to 2 psi over the recommended pressure, and might as well get an alignment as I haven't had one in a while.

I was just hoping that other than being very cautious about acceleration, etc., that something changed for the 2011 model year that made the engine slightly more efficient as indicated by the posted MPG for that model year. Possibly, whatever the change may be, I could implement that for my car at a reasonable price to achieve slightly better fuel economy.

I agree with the recommendation that a $1000 chip that does give you a little better gas mileage just isn't worth it as the payback period is extremely long.

Thanks!