when i first got the car i was babying it around until i got used to it, which yielded something like 15mpg with a good mix of traffic and highway twice daily. later, it fell to about 12mpg when i just started driving it -- same route.

now the world has changed, and it isn't really comparable to back then. i have no commute, and i make up reasons to go drive the car almost every single day, and they are all of the "in and around town" sort. i did a hard reset recently, and i've been watching the "auto" mpg mode instead of trip A or B so no long-term compilation of data. when i pull in the driveway after a 10-minute drive sometimes it says 10mpg and sometimes it says 6mpg.

 

I don't normally check the gas mileage, I was just curious how good it might be on a highway trip. Around the back roads I think I get @ 16~18.
wj

 

Like many of us, I don't much care about fuel economy for the cost. I'm just curious about how the car runs that causes it to get to relatively low mileage.

 

Have you checked for DTCs?

 

I haven't gone any deeper than the first layer of stored codes and it is clear.
I have a foxwell nt630.
wj

 

Your 2008 is 15 years old. If it has the original catalytic converters, they may be starting to get clogged up even if you don't have a CEL. That can reduce MPG.

 

no question about that, in my case, only if something dramatic changes will I be spending the time+effort+$ to get better performance (other than the handling). MY end game is a 14-15 xkr(s).
wj

 

Try just giving it a good hard rip. The 'ole Italian Tuneup can help a lot when a car's been tiptoeing around town for short trips for most of its life. You bought the car; go use it.

 

The only time the Italian Tune-up worked for me was after I had new pistons installed in a Honda CBX motorcycle that just happened to be turbocharged.

I picked it up from the machine shop and loaded it in my truck for a trip into the Texas Hill Country. Unloaded, excited beyond belief and then I drove it. I was so disappointed, I had lower compression slugs installed and my first thought was that I went too low, it was a cow. I pulled over, considered the situation and then took it out and nailed it in first, second and I was about to cry when low and behold that sixth cylinder started firing. Those bikes had terrible frames, let's just say that instead of it pulling a wheelie at speed it laid down a strip of rubber at 85mph. I suspect that there was a metal shard shorting out the electrode but whatever, it worked.

That was my only successful Italian tune-up all other attempts simply used more fuel.

wj

 

Italian tune ups work better on old engines that are caked up with carbon.

CBX... I'm jealous. When I rode, I had a CBX engine in my garage while I was finishing up an ST1300 naked build. Before I had a chance to do anything with it, I moved and decided to sell it. And the wet noodle UJM-era frames were just the worst. I've only ridden my Titan once and even at legal speeds, it'd take three lines through the turns- the line the front end took, the line the rear end took, and the line you thought you were going to take. Also... Those brakes...

 

Weird as I've gotten 32 (IMP) MPG on long runs with cruise set to 75, that equates to 25.5 (USA) MPG

But then mine is 5.0 and apparently (?) more economical.

Current price of unleaded fuel here in the UK is £1.60 or £7.13 IMP gallon which I think works out at $7.81 per US Gallon taking into account yours is 17% smaller.

 

I think the ST1300 could have been the world's most perfect bike. Had it not been so top-heavy, I may not have sold mine in favor of a Goldwing.
Having said that, I read your reply intently and just burst out laughing when I got to "Also.... those brakes..."

 

My 2011 XK can get 25-26 mpg while highway cruising, and keeping it around 65 mph. As soon as you get off the highway, its much harder to get decent mileage... i probably get 16 mpg without trying to save gas.

 

Just completed a 5000km (3106 miles) drive over 6 weeks around the South Island of New Zealand and the XK recorded 10.1 KM per Liter, which is 23.75 miles per US gallon, or 28.5 miles per gallon UK

 

I was scanning the thread when I saw your post.
I recently tried on my dress tunic that I last wore with pride in 1994. Amazing how much it's shrunk since then.
I worry about not be able to get myself out of the back seat of The Jaaagg if I try to install Jagwrangler's Magic Top Down Module.

Now to what I wanted to post.
When we bought the 2007 XK convertible in December we were getting 21-22 mpg.
About 54K on the odometer. Mrs. P drives it to work most days, about an 8 mile round trip. Occasionally, I get to take it out on I-75 for a 100 mile spin to work in Tampa and back home.

Normally I'm like a lot of you who wouldn't care about mpg, but today I put 14.2 gallons of Shell premium at $5.45/gallon with a 25 cent/gallon discount. $77.43 total!

The numbers showing up on the dashboard display are concerning. But it's the 15 mph average speed (not even in a parking lot) that has me wondering if there's a fault in there.

 

Looks like mine. As for the 13, could you or the wife have been sitting idling the engine, enjoying the AC. When I take my wife to the grocery store, I wait in the car while she shops, fuel mileage will look about like the 13 you see. The only time I see 22 to 25 is on the highway.

 

LOL. Trust me, the Mrs. ain't sitting idling the engine.

 

15 MPH average speed suggests a lot of stop-and-go driving. Being stopped in traffic with your engine idling is zero MPG, which really hurts your average MPG.

Ask me how I know.

 

I've heard the horror stories of Atlanta traffic. It's nuts down here too, especially getting used to 4-5 minute waits at traffic lights.

Did a reset before driving home from Tampa last night and averaged 25-26 mpg with the cruise set at 86, I'll take that any day of the week.

 

XKRs have mileage? Huh. I totally ignore all that. When the fuel gauge goes low, I refill the tank.