Poor MPG for my 2006 2.5T S60 at 89K

[EngineeringBloke]

I get between 12 and 15 MPG on my commute into work. Lots of traffic lights and heavy going for 8 miles. Still, even with an easier return on the highway in the evening, that seldom gets more than 16 - 18 MPG. Easy weekends I see about 20 MPG with non-spirited driving. When I do long distance highway, I usually only get about 24 or so. I think I should be getting better than this.

So I think something is not right but I have not been able to track it down. Car is third hand, so I did not see it new but I have had it since 2009 (with 30K miles). I record fill ups and mileage in a spreadsheet, I review the MPG and reset one odometer each fill, and the other each trip.

MPG has gone down a little since 2009 but it was not great then. I have seen some improvements in performance with sensor cleaning, but not much change in MPG.

I have new NKG plugs (had new Volvo ones before), IPD coils, Volvo engine air filter, cleaned MAF with MAF cleaner, had a mechanic clean the MAP (cos I could not remove the retaining screw myself), IPD TCV, new battery, had gummy oil trap hose fixed, I changed the ATF using the drain via cooler line method), replaced the fuel filter, did the oil filler glove test for PCV and glove is pulled in indicating good vacuum/PCV.

I ran Techron injector cleaner several times in the gas.

I use the Android Torque app - no codes stored, no check engine lights. The front wideband O2 sensor does not move much, except when I take my foot off the gas, and then it shoots up for a bit. The downstream O2 cycles each 10 seconds - I expect cycling in the downstream but do not know if this is too slow - anyway this is just a test of the cat efficiency so I think it is OK. The ST fuel trim and LT FT are low values. A/F is around 14:1 - fluctuates a bit.

Car enters Closed Loop operation within 5 minutes or so.

I have not identified any vacuum leaks but only did a visual inspection, and could not hear anything either.

Fuel pressure seems to be 43 psi whenever I check it on Torque.

I notice that my throttle never seems to close below 12% even at idle (about 670 RPM). This seems too open to me. I wonder if dirt or worn throttle gears are an issue. Perhaps after the issue with the Marinetti throttles, the engine control unit was made less sensitive to errors. I do not had VIDA so cannot check for warnings that are not CEL codes.

Dealer and my independent Volvo mechanic say they do not see anything wrong. But I also don't think I have great acceleration - 0-60 spec'ed at 7.3 seconds, and I think I get closer to 9. That would be an issue with boost, and is probably separate from the MPG aspect.

Tomorrow, I am having some suspension work done, and will have the upstream O2 sensor replaced. I just want to remove that as an issue.

I am looking for ideas on what to focus on next:
- search for a vacuum leak
- check turbo wastegate adjustment
- replace PCV
- clean/replace throttle body
- clean/replace fuel injectors
- buy VIDA and check control units for errors and warnings

- or anything else?

I'd appreciate any insights you have.

Thanks,
Simon

[vtl]

I have 18.8 MPG right now, driving in suburbs with light traffic. Never ever seen anything above 22.9 MPG. Usually get about 21 MPG on highways in summer.

FWD V70 with 2.4l N/A engine had about same consumption, maybe only marginally better. 2.5 with direct injection in wife's new XC60 is maybe 1-1.5 MPG better in the same traffic.

Poor acceleration can be related to thin ATF: you can get official numbers only on a fresh original ATF (and everything else properly working, of course). But I was surprised how much more torque Volvo ATF transfers compared to different mixes of Mobil/Idemitsu/Valvoline/Aisin/Amsoil I had before.

What oil you run on? My mileage dropped a lot after replacing 75w90 with 75w140 in bevel gear and 5w30 with 10w40 in engine.

[precopster]

In my well maintained 2001 T5 I get 16.8US mpg or 14L/100kms with some traffic and highway combined. She has 137 k miles.

On a long trip I can get 23.5mpg with no traffic and 60mph

Just had all oils replaced, new spark plugs and reconditioned head. Very low oil usage.

These turbo cars are NOT frugal.

[mrbrian200]

These turbo cars are NOT frugal.

Not necessarily. I just did that (map below) on 2.8 gallons of premium just hours ago--112 miles/40MPG.

MY06 FWD S60 2.5T 104k mi on the ticker. Some stoplights/stop and go on both ends and through downtown South Bend: not strictly highway.

Hints: on the FWDs @60mph if you're not coasting the downside of highway overpasses with your foot off the gas and instant econ at least in the 70s, often pegged at 99, you've got parasitic drag--either dragging brakes, alignment, or ridiculously high rolling resistance tires. In heavy inner city rush hour 'creep along' you should be touching the gas pedal with a feather momentarily and coasting most of the time unless you're pointed uphill.
Alignment is 80% of the battle on these if you're looking for great econ. I've learned you can't rely on 'shop machines'. You have to play with it with some trial and error involved. Some shops will road test and fine tune after a basic machine aided setting. This can take hours. For $59.95? Not gonna happen.

Or you have problems. NO CEL does not mean it's running perfect.

No ICE car on the planet with a powerplant over 100hp will get good econ in stop and go if you're a leadfoot. I can burn up 1/8 tank on gas just on a 10 mile round trip just to fetch Starbucks. These cars feel wonderful when you stomp on it. Even just half way down.. I love it too. But I've learned to back off: that same 1/8 tank can get me more than half way to Chicago (100+ miles away) if I just take it easy. NO, nobody's yelling at me for going slow. Feather plus a little is still as fast/faster than most people in average non turbo cars accelerate from a stop. Anything past about 1/3 throttle on these is the equivalent to a Honda Civic being driven really hard. We lose this awareness because we're acclimated to so much more... when the Civic would be straining at the redline and sounding like it might blow up (most people would back off unless they're genuinely in a hurry), these Volvos don't act like they're even trying. 'VOLVO driver' and the LEADFOOT are interchangeable terms to non-VOLVO owners, just as a reminder. Other people don't realize we're barely touching the pedal. From their perspective we must be flooring it. Power=fuel consumption, even though the car doesn't act/sound like you're driving it hard/agressive, you just might be.

Anyway--
The S60 has a drag coefficient of 0.28. Yes they CAN do it or at least the FWDs can. Everything has to be purrrrfect. And exchange the 2 pound lead weight for something more of the 8 ounce variety.

[oragex]

0-60 in 9sec is certainly not normal on the 2.5T and 17mpg highway is way too low at 55-60mph. Cleaning the tb is not a bad idea but not that easy on the turbo engine. Not sure about replacing the front O2 but if you go that way make sure to use the correct brand and don't discard the old one
I would rather say there's an issue related to the turbo or one of its hoses, but I'm not knowledgeable into this area.

[JRL]

I average about 15 MPG
Mostly stop and go
My latt tank was nearly 20 MPG because I did two 50 mile round trips (200 miles on the PA Turnpike at 70)

[chrism]

If you're judging your mileage by the onboard computer, please know that those things aren't perfectly accurate. On our cars the computer reports about 1-2 less MPG than if I do the math using miles traveled divided by gallons purchased at the pump.

However, that being said.....

Both our 2003 V70 2.4 NA and 2005 S80 2.5T do about 20 city / 29 hwy (usually heavily loaded at 80 MPH). I run the tires at about 40-42 lbs. A/C is usually on. I use Walmart 10-30 synthetic oil changed at 5,000 mile intervals and change the trans fluid at 30-40,000 miles with Mobil 3309.

You say acceleration doesn't seem strong enough. I'm wondering if your cam timing is a tooth off, in which case you would "expect" a CEL, or if a VVT isn't fully advancing.

Also, have you checked to make sure the PCV is pulling vacuum as it should? These cars seem to not like it when the PCV system is obstructed.

[850TurboTurtle]

For reference, I recently got 32+ mpg on my 2006 S80 with twin turbo on a 250 mile road cruise at 65mph. Same week I got about 17mpg around town not driving too hard, back and forth to grocery store, church, etc. (Verified with mileage divided by topping off again, trip computer accurate to half a mpg)

My guess is the heavier sedans eat a lot of fuel getting up to speed and then stay there easily.

A slipping transmission would eat a lot of fuel too, especially in city driving.

[850TurboTurtle]

My mileage dropped a lot after replacing 75w90 with 75w140 in bevel gear and 5w30 with 10w40 in engine.

Do you mean mileage got better or worse after the oil changes?

[mrbrian200]

If you're judging your mileage by the onboard computer, please know that those things aren't perfectly accurate. On our cars the computer reports about 1-2 less MPG than if I do the math using miles traveled divided by gallons purchased at the pump.

The more you tweak tires/suspension etc. for higher mileage, the further the average mileage number on the onboard computer is off.
The average-o-meter is 8-12 MPG low on mine from actual observed econ (tracking fuel purchases and miles traveled), even if I reset it before a long drive I've never seen it more than 32 mpg.
The average appears to be a complex calculation which seems to 'under-weight' stretches of coasting downhill with the pedal fully released, and/or in heavy traffic when the wake from the vehicle directly in front pushes cruising econ well into the mid/high 40s. It's like the computer decides 'impossible!' and factors some lower number deemed more realistic into the average.

However, the instant econ does appear to be pretty accurate. If I watch the instant and guestimate what the average might be, the number I come up with clicks with what I'm actually getting.

Be aware if your car is AWD you will never see these numbers. The AWD system (angle gear, driveshaft, rear diff and extra set of halfshafts) adds a crap ton of rotating mass into the drivetrain and substantial parasitic losses. AWD I believe the best case you can hope for is somewhere around 30-32 at moderate speeds. High speed interstate travel at 75+ mph you might not even get 20.

I'm very interested in the technical details of how the new SPA T8 drivetrain behaves (FWD + electric rear drive). If its not 'full time' it's potentially a way to add AWD without all the losses associated with driving the rear wheels mechanically off the trans. When I was looking for a S60 I specifically ruled out AWD ones. You couldn't have given me one I would have just sold it and used the money to buy a FWD.