1999 V70 XC Poor Fuel Mileage or is this correct?

mctee · Post by **mctee** » 28 Nov 2014, 20:00

1999 V70 XC Canadian car with 354,555 km. I have been working extensively on it to catch up on maintenance and return to "stage 0".

My Combination city/highway mileage is coming in at 13.4L/100km (+/- 21 MPG) driving it real easy.

My son's 1998 V70R is averaging 11.6L/100km.
My three previous R ' s ('04, '05, '07 all 6spd) all averaged 10.5 to 12.0L/100. Newer yes, but way more power and usually drove them way harder.

Compression tested 13 to 14 bar (yes, I know, seems high but old gauge of very good quality from my dad, I think) across all cylinders and head gasket / valves were done 100,000 Km ago.

Recent work completed:
- PVC system complete with sump off to clean out PCV drain plus change sump o - rings
- Timing belt and water pump
- Air filter
- Fuel filter
- Spark plugs
- Cleaned ETM throttle body
- New used turbo (way less km! )
- New pre and post O2 sensors
- New welded in catalytic converter
- New used rear exhaust assembly (no holes!)
- Exhaust manifold off for a few helicoil inserts and new gaskets
- Re-welded downpipe flange
- Cleaned MAF

I am reluctant to change out any more parts (what's left other than MAF and ETM?) plus I am NOT GETTING ANY CODES and runs pretty good. Just seems very thirsty...

What is the mileage you are getting in either MPG or L/100?

Any ideas or suggestions or is this as good as I am going to see?

Post by **misha** » 29 Nov 2014, 05:29

mctee wrote:My Combination city/highway mileage is coming in at 13.4L/100km (+/- 21 MPG) driving it real easy.

Completelly normal for these cars.
My 850 with auto transmission have the same consumption.Sometimes it goes up to 15l/100km of city driving.On the freeway it's around 8-10l/100km at around 120-140km/h.
I bought it almost new,back in 2000,and it always had the same average consumption.

Post by **oragex** » 29 Nov 2014, 05:49

I might be wrong, but I think it's a bit high. You should get that mileage in city only driving. If driving only on highway, I would expect well bellow 10l/100km, more like around 8.

I don't see the thermostat in the list. Does the upper radiator hose became warm shortly after start up with cold engine?

One other factor can be clogged injectors from fuel varnish deposit (especially if the car was always driven smoothly and the gas didn't have good detergents-cheaper brands, or if the car wasn't used for a while). Ebay sellers offer efficient cleaning for around $100

The engine acceleration is normal? Is the idle smooth? What front oxygen sensor did you use?

Also watch for a vacuum especially at the gaskets used after replacing the pcv - such as the intake one

Finally, how is the transmission fluid ? If it's been replaced, was the transmission software reset to new fluid? I think it can impact the mileage.

Post by **mecheng** » 29 Nov 2014, 06:57

You can't compare combination, because what combination of each?

For my s70: I get 7.5l on highway
12l in city. That is in the summer, full stage 0 but with a bad front O2 sensor which I replaced now.

What brand of O2 and Maf do you have? How's the cap/rotor

Considering the power I have on tap and vintage of technology I'm very happy with the numbers especially highway which I can get down to high 6s but driving like grandma

Post by **misha** » 29 Nov 2014, 07:29

oragex wrote:...how is the transmission fluid ? If it's been replaced, was the transmission software reset to new fluid?...

What?

instarx · Post by **instarx** » 29 Nov 2014, 12:10

I think 13.4L/100km is a bit high for combined city/hyw usage. My lifetime usage city/hyw is 10.8L/100k.

13.4 L/100km isn't 21 MPG, its only 17.5 MPG (US Gallons). I get 17+ for suburban driving alone in the winter. A little better in the summer.

mctee · Post by **mctee** » 29 Nov 2014, 15:39

Thanks to all for the input!

Yes, instarx, you are correct that I converted to Imp gallon vs. US gallon.
See how us CDN's get 20% better MPG just by being north of the border? 1.0 Imp gallon = 1.2 US... Never mind...

On a straight free way type trip the average goes down considerably to 9.5-10.0/L 100km. It is definitely the stop / start that considerably up's the consumption to more than my expectation.

I don't see the thermostat in the list. Does the upper radiator hose became warm shortly after start up with cold engine?
Correct, I did not do the thermostat but warm up is quick and yes, the hose gets warm very shortly after start up.

The engine acceleration is normal? Is the idle smooth? What front oxygen sensor did you use?
I was thinking the acceleration is normal but after considering your question, intial acceleration from dead stop does seem a little "strained" or "chugs" slightly - not as smooth/quick as it should be. Perhaps from idle to +/-2,000 RPM. Then seems to clean up and run through the RPM stronger. Pulls hard on WOT right thru to redline.
Idle is very smooth with no jumping. No ETM codes.
Pre and post O2 sensors (both were likely originals) were replaced with NTK (NGK) brand. Not Bosch. As I noted, there was an immediate improvement in both performance and fuel mileage when I replaced the cat and the O2 sensors. From just standing behind the car you could immediately tell that the exhaust was definitely rich. After replacement the exhaust smell is very normal / not rich smelling.

Also watch for a vacuum especially at the gaskets used after replacing the pcv - such as the intake one
I'll look closely at all potential vacuum leak areas.

What brand of O2 and Maf do you have? How's the cap/rotor
New O2 sensors are NTK brand which is NGK.
MAF is a Bosch part. Upon cleaning and inspection I did notice that on the back side (downstream) of MAF the seal is broken. I ordered a MAF from IPD yesterday on their Black Friday Sale!
No cap / rotor - it is a '99 car.

I'll install the new MAF next week plus have a better look at the fuel injectors as I think they are originals, too. I gave them a good cleaning / inspection when I did the PCV system, but...
I am seriously thinking of installing a bung in the downpipe to temporarily run a wideband just to get a really good look at what the air fuel ratio is at various throttle opening and loads. I think this would be the most accurate way to ID a potential rich condition (like perhaps just off idle?).

Post by **oragex** » 29 Nov 2014, 15:56

mctee wrote:Thanks to all for the input!
[/i] Correct, I did not do the thermostat but warm up is quick and yes, the hose gets warm very shortly after start up.

This actually means the t-stat is stuck open. Starting with a cold engine, the upper hose should stay cold for quite a few minutes, until the stat finally opens. On the other hand, I don't think this is the reason for the low mileage, it surely affects it, but not that much. However, an open stuck stat is not good for the mixture ignition and possibly for the combustion chamber temperature, and it's cheap to replace.

The transmission level is good? Was the fluid recently replaced? I noticed on my car, after I replaced the fluid the mileage dropped, my guess is because the software has to be reset afterwards (it does affect quite a bit the shifting pattern).

JeffHicks · Post by **JeffHicks** » 29 Nov 2014, 16:10

For what it's worth, I get about 27-28 highway mpg out of my 1999 V70 fwd. I get about 24 highway mpg out of my 2002 XC70 awd.

Combined economy depends entirely on the weather and what combination of driving I do.

mctee · Post by **mctee** » 01 Dec 2014, 20:23

Thermostat was replaced July '09 (90,000 kms ago) with a Volvo part #271664.
I think it is fine and car warms up quickly plus temp is rock solid from -10'C to +30'C. But that is significant time and mileage so I'll do it this week along with MAF and heater core and o-rings. Process of elimination...