Engine: B8444S: 2007 XC90 4.4 Fuel consumption difference.

[HunterBruce]

I have two 2007 V8 doing an experiment on improvement on fuel economy.

On highway at 70-80MPH getting 24-25 MPH on one and 25-26 MPH on the other both on Petrol.

4% Difference. I wonder why, have any of you got idea's pls.

Diff Tires. (Same) 20 - Not
Brake binding slightly -Checked.
Wheel bearings. ?
Any other factors, any ideas to check welcome?

Thanks.

FYI - The higher mileage one is better. Both have had recent service.

[TruckbusUK]

Fuel injection and other "engine management" related software ... Volvo updates the software on the cars all the time, when was the last time any of the cars had been dealer serviced (FOC software is updated under the "service promise" every time the car is dealer serviced,) the cars could be running different software levels.
Plus
CAT, MAF, valve clearances .... most of the stuff you would check at a service fuel filters, air filters etc

Where to start. not exhaustive and maybe not relevent to the V8's but something to think about.

Edit, also have you had the codes read using VIDA, there may be a pointer there.

[HunterBruce]

Thks I'll look into.

Will wheel bearings make a difference?

[Familyman 90]

Unless they were manufactured together, on the same tooling with the same level of use on that tooling, bought at the same time, driven and serviced utterly identically, they will not perorm identically. Even then, vehicles manufactured as identically as it is humanly possible to do can still differ in output, and therefore economy for a given level of output, by as much as 5%, due to cumulative differences in manufacturing tolerances. Yours is well within this known variance.

Comparisons about any aspect of the engines function is therefore meaningless.

The higher mileage one may be more economical, but no valid conclusions can be drawn as to the reason(s) for this as we have no control sample.

I can understand keeping a vehicle well maintained and efficient, and applaud and encourage that. However, beyond that level anyone with even a remote interest in fuel economy would do well to avoid 2.2 tonne SUV's with poor aerodynamics and draggy drivetrains, particularly those with 4.4 V8 engines.

[TruckbusUK]

Originally Posted by HunterBruce

Will wheel bearings make a difference?

If they are not binding/rough or shot and very noisy I wouldn't think so, but I may be wrong.

On the XC90 they are incredibly difficult to pinpoint, usually a drone that gets worse as the car corners and the weight loads and unloads as it shifts in the manoeuvre. the 2007 cars onward had a new design of bearing where the seal was improved reducing water ingress to the bearing, so I'm not sure unless you have noise that your bearings are the culprit.

[HunterBruce]

Thanks this is most helpful. No real noise.

I looked through my last service when I bought the older miles XC90 I had premium new Iridium spark installed ready for LPG. So this maybe one reason.

[HunterBruce]

Yes its a bugger having V8 MPG.

But I need an affordable big strong safe car to tow many miles.

I can think of no other.

LPG - would be away round high cost, esp if I had on farm for other uses and buy in bulk.

[SwissXC90]

I once had a 4.4L V8 BMW 5-series, utter luxury.

My fuel economy was IDontGiveADamn MPG

[HunterBruce]

Anyone pls know which are the best Spark plugs for XC90 v8 4.4L ?

[Rich850R]

Why is even fuel economy a factor driving and XC90, my word people get a grip