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New (to me) car maintenance regiment to help MPG?

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Just picked up a new-to-me 2006 OB 2.5 LTD 5 speed a few weeks ago. It's in pretty nice shape, 110k miles, needs a few things addressed; worst are ripped inner CV boots, alignment gently pulls to the passenger side, may(?) have a rear wheel bearing to address in the future, but otherwise is really in good shape.

I have an Ultragauge hooked up now, and am getting 24-ish mpg* ... was really hoping for closer to 27-28 since I drive mostly highway and thought it should be possible since my wife's 2010 OB with the 2.5 & CVT does 30-32 on the highway.

What would be a good regiment of maintenance items to try to tune / increase fuel efficiency?

*Note that getting this kind of mpg feels a bit rough, just coming from a Toyota Echo that regularly gets 45 mpg with little effort.
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2001 VDC Wagon - White pearl - 302,000 km
466 Posts
A bad wheel bearing can cause a fairly substantial drag at higher speeds. Best to address that (along with the CV boots) first. It doesn't seem logical, but it may be the cause of your slight pull. Either way, a misalignment creates rolling resistance. Tires can play a huge part in mileage. Read the forums here to see about mileage improvements from different tire brands. TBH, most 2nd or 3rd gen OB owners seem generally acceptive to get something close to 25 mpg. Please don't compare a Toyota Echo to an Outback ever again please lol.

Super Moderator
2008 OB Limited 2.5i, Portland OR USA
10,608 Posts
My 2008 with 2.5i NA, automatic, and similar miles can still do 28-29 MPG on long highway stretches and reasonable speeds (60-65). Higher speeds will drop it down 3-4 MPG. A cartopper will drop it a couple. And as soon as you're in start stop traffic or just going about normal errands around town, it will drop to 23-24. Doing short trips only were it never fully warms up puts a 3-4 MPH hit on. Winter fuels put another hit on top of these.

These are not necessarily cumulative, but what I'm saying is that it seems like if you get anything off the ideal conditions, it will drop you 5-6 MPG off the maximum economy pretty fast. You can do a few things, some already mentioned here, and these can all add up to help a little. I would focus on whatever is making it pull right; that could get you a double return (tires and MPG). Some others are:

- Tire air pressures will make a big difference; keep those in spec
- Oil changed per schedule
- Air filter should be replaced if doubtful
- Wiih the MT, check that the clutch is not slipping
- No brake parts dragging
- Shed any extra weight - it's amazing to me that some will routinely carry a couple hundred pounds of crap in their car, thinking that they may need it on the road.

On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
28,319 Posts
agree with the above posters. 5w30 oil is what that car calls for.
(a happy year round oil, that is on the thin side, others that are thicker may slow the car, and not flow as easy when cold in winter).

plus avoid idling = zero mpg for those periods really draws down your average observed mpg fast. if you think you are going to be stopped for more then a minute shut the engine off.

windows down A/C off when going under 45mph, windows up A/C on when going over 45mph. (wind resistance vs. A/C drag on that engine)

OBW H6 VDC, Tribeca, XT6
12,391 Posts

Redo all your brakes: Brakes can drag enough to reduce mileage but cause no symptoms. Could the "rear bearing noise" you hear be rear brakes dragging? It's usually pins and/or clips that cause brake issues and they typically get the least attention from average DIY and even shops often times:

1. throw away the slider pin bushings and use high quality grease from subaru, SilGlyde or equivalent.
2. replace all the brake pad clips - or just buy a high end pad kit from subaru or others that includes the clips. these routinely build up brake dust, bend, or corroded and keep pads from moving freely - which means they can slightly ride on the rotors.
3. install whatever pads you want and bleed if needed. Subaru rotors never need replaced, don't even look at them, unless they're vibrating when braking from a high speed. Then replace the one rotor that's vibrating.

Oxygen sensor. You could try to test it's output and see what it looks like if you like playing with gadgets and getting technical. Or just replace it. I figure for the 300,000 miles I want out of mine I might as well just plan on replacing the thing once around 150k and be done with it.

Seafoam the intake and add MMO to oil/gas whatever the directions say.

These are actually unlikely culprits but I just time all these together and sometimes times like this are a good reason to just get all the simple/routine stuff done:

Air filter and PCV valve (it's unlikely needed but cheap, easy and i like to time it with some other maintenance).
Plugs and wires - they're not really problematic on this engine or they'll give you a check engine light for a cylinder misfire if they are, so they're not at all necessar

Issues you reported, get your alignment but I'd do the other items first:
1. If they're OEM axles, reboot them (absolutely do not replace)
2. Inspect rear wheel bearing - maybe it's brakes dragging?
3. Replace wheel bearing or address brakes
4. Alignment - i would have that done after the CV, rear bearing/brake work.
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