mileage update, if anyone is interested

roadtrip to vegas, 99% highway miles at relatively high speed, 22 mpg. highest speed achieved; 117 mph....


next tank was back home, mixed highway/town; 18.5 mpg

 

Road trip today from Canberra to Sydney and back (in Australia): about 600km round trip (okay, that's 400 miles for those that can't convert).

Best on trip? A staggering 4.2 litres per 100km from Marulan to Sydney (167 km, or 100 miles) That's about 56mpg (US) or 67 mpg (everywhere else).

Average overall - 5.1 litres per 100 km (46 [US] or 55 [everywhere else] mpg).

Not bad for an average speed of 105kmh in a 3.0 litre diesel MY12 XF.

 

370 miles would be a closer estimate 8-)

Canadians remain bilingual as we often travel to the US. Our speedos are usually marked with both and electronic trip computers can be switched to display metric(SI), US or "imperial" units.

Converting mileage in mpg to fuel consumption in l/100 km is a nuisance. Fuel consumption is a more logical measure: quarts per 100 miles.

Interestingly, I don't think anyone uses the old Imperial gallon now.

Those turbo diesels certainly don't use much fuel. I'm wondering how my new V6 SC gasoline engine will compare to my 4.2 V8. Fuel tank is the same so back to back comparisons will be a doddle. Stop/start is also fitted which works during our summer but will not be active for most of the winter

 

My previous 2010 5.0 NA averaged 16.7mpg over 18,000 miles. Best observed highway trip was 28mpg.

My current 2011 5.0 S/C average is 15.6mpg over the last 20,000 miles so far. best observed highway trip is 24mpg so far

 

My 2012 sc says average 15.9 mpg which I find appealing now lol

 

The distance I travelled was actually 641 kilometres (398 miles), but I wasn't making a point about the distance, rather the fuel consumption.

 

Whilst I'm here, why is my Garage empty? My profile shows that I own a Jaguar XF 3.0D Premium Luxury, but when I choose 'Add now', nothing allows me to edit this and show what I own. Or is the forum broken?

 

You might want to repost this in the technical help section at the beginning of the forums.

 

My 2010 4.2l N/A XF seems to average around 29.9 or 29.8 / US gal on interstates for trips of 250 miles plus and 22 for local Milage, not bad eh!

 

Does anyone else notice a big difference in the winter. My 2010 XF SC was averaging 15.5mpg very consistently for my mostly highway driving commute to work in the winter (with winter tyres). Since the weather in the new england area warmed up, I'm now around 18mpg consistently (still got winter tyres on).

I've not managed to get it above 20mpg even for highway cruising on long trips though

 

How about tires ! Since getting rid of the original Pirellis and putting on new Michellin Super Sports and after about 300 miles for break-in, my mileage for both city and highway has dropped 2 mpg. I thought that it would improve. I drive a 09 XF/SC

 

The Michellin Super Sports are a softer compound. Better handling and grip, but more rolling resistance.

 

Now wait a minute......does that also mean that the tires will wear down faster, getting fewer miles ? From all the reviews I read including Tire Rack, these tires should get a lot more miles on them than the Pirellis. Am I wrong ?

 

Warmer weather = higher pressure in the tires = better milage.

 

Mine is not S/C, but highway for the 5.0 N/A is about 24-25 for me. I could get 29-31 out of my 4.2 XJ!!

 

Cold weather burns more fuel. This is the biggest factor, longer warm up means higher consumption. No way around this. Driving in snow burns more fuel also.

Also, because of temperature adjusted fuel delivery you actually get less fuel in winter. Fuel should be sold by mass, which relates directly to energy content, and is independent of volume. Fuel is actually sold by volume which must be temperature adjusted to allow for lower density in warmer weather. Our gasoline is adjusted to 15C. The adjustment isn't perfect and the fuel contains a higher percentage of volatiles which have lower energy content. Often ethanol content goes up for winter.

Tire pressure need not make a difference as you should add air for cold weather to keep the measured pressure at spec. If you do so then you actually drive with higher pressure for most of the winter than you would for summer.

 

Thanks Jagular. I did a bit of research on this as it's an interesting question. It looks like the major driver is the engine warm-up and inefficiency until it's at operating temperature due to increased friction in all the moving parts. There is apparently also about 20% more drag on the tyres on very cold days, and even the air density can make a difference (apparently upto ~7% on a very cold day at highway speeds). As you say, snow would of course make a major difference on top of all of that. Let's see how it does as the weather warms up some more.

 

Interestingly, the denser air increases pumping losses past the throttle plate on gasoline engines but not diesels. The reason is more air is drawn in at any given throttle position due to higher density. The engine makes the same power but at smaller throttle angles. Paradoxical though this may seem. More peak torque is not available because peak torque is limited by combustion chamber pressure which cannot exceed a certain level at full throttle. So, full throttle performance will not be affected but part throttle will deliver lower fuel efficiency in cold weather!

 

I've got 19K or so miles on a set super sports that a transferred from my previous XF S/C to my current one and there is hardly any wear. Should last at least another 20K miles. I'm getting about 24.6 to 25.5 highway MPG from my current XF S/C per the vehicles trip computer.

 

Interesting......what pressure do you use in the Michelins ? I am using the mfg recommended 34 psi. I actually haven't seen a big difference between the Pirellis and the Michelins in all respects.....maybe a slightly more comfortable ride.