What are your best tips for this?

I saw that Mad Max had an on/off switch on his supercharger last night, that would save some gas eh? Anyone tried that?

I have seen magnetic gizmos that clap onto your gas line claiming to "align" the gas molecules and add 5%+ to your fuel efficiency, any truth to it?

I have the American XJR any sort of exhaust tweaks that would help? How much can an air filter help?

 

Fenja:
Gasoline molecules do not align. period.
Work out the math. If you drive 15,000 miles per year (a lot for a 15 year old car) . Your annual fuel usage is about 750 gallons. Thats now about $2,500. IF (big if) you improve mileage 10%, you have an annual savings of $250.00. Future value math at today's low interest might give you maybe 3 to 4 years of cost saving. So, if you can gaurantee a saving of 10%, then spend less than $1,000. for the improvement. I know of no aftermarket stuff that either guarantees that or costs less than $1000.
In todays closed loop systems, the air filter is not as important as it once was. In a carb car, the flow restriction wiould seriously affect the performance. Feedback systems correct for that.
Now, as to the supercharger. I suspect that with the supercharger disabled, you drive much less "spiritedly". I know that I get much better mileage when I am watching it for about the same reason.
Things on the Jag that are important are no exhaust manifold leaks, clean MAF, good lamda sensors.
Oh, and tire pressure. According to our president, in a campaign speech, just inflating our tires (with tune-ups) will save more than 1%of gas usage. Thats one thing hes got right.

 

The biggest factor is the right foot! Also, tire pressure, tune-ups and make sure your car is running right. These are older cars and the O2 do have a shelf life. I fould out mine has faulty down stream O2s and is only getting about 14 MPG. I only get a check engine light every couple weeks.

 

Should I check my o2 sensors because I too get about 14 mpg in my xj6. Whats the average for a 96 xj6?
________
Erect ****

 

City :17
Highway : 25 MPG . Fuel saver kits are totally gimmicks each time I ask this question I get same answer despite "customer satisfaction reports"

 

don't forget your lucas injector cleaner!

on sale at autozone right now
(no affiliation, I quit a few months ago)

I find it makes a difference.
but you generally don't see an increase in mileage until the next tankful.

14mpg is about on par with what an XJR makes,

but my XJ6 makes atleast 15-18 around town and 20-25 at around 70mph on the freeway depending on how much throttle I give her

 

14.7MPG around town with a little highway mileage here in my '96 XJ6. New tires, perfectly aligned, good tire pressure, clean EGR, new oil filter, new air filter, new spark plugs, Lucas injector cleaner. Would a new fuel filter or anything else help?

 

yes, a new fuel filter would help.
I only run 93 octane, and clean your MAF with MAF cleaner

 

Okay, I'll have to have my mechanic do that for me as I've heard you get covered in gasoline . What part of the MAF do I clean? I always run BP 93 Octane also.

 

If I'm careful I can manage 23 mpg/highway out of my XJR. (That's about 27 mpg for your guys over in old blighty <grin>)

It, just like my previous two Jags, seems to hit a wall at 70 mph, though. Economy drops off significantly at 70.0001 mph. Anyone else experience the same?

Cheers
DD

 

Wow, that's actually really impressive for such a large vehicle with a supercharger!

 

that is impressive!
my XJR got terrible mileage, but I'm sure it had fuel issues.

and the MAF sensor has two little prongs for lack of a better description, just shoot those with the cleaner. they're like the only thing inside the sensor housing.

 

Gotcha. I'll have to go buy some MAF cleaner, clean that off, replace the fuel filter and maybe my air filter even though it looks decently clean....then we'll see how my MPGs react.

 

Rookie question, what are MAF and EGR?

 

MAF = Mass Airflow Sensor

EGR = Exhaust Gas Recirculation valve

I think it'd be snazzy if there was an EGR delete kit for our vehicles.

such a waste of exhaust plumbing and we wouldn't have to have exhaust gas being put back into our intake manifolds.

cleaner valves, and exhaust stays true to its nomenclature,
exhausted resources having already been burned.
don't listen to me I'm just complaining

 

My XJR doesn't have an EGR :-). For whatever reason they weren't used on 1995 XJR/6s. Not sure about '96 and '97 XJRs, though

Cheers
DD

 

I'll re-emphasize the "If I'm careful" remark.

If I drive the car they way it was intended to be driven (leading the pack, not dawdling along choking on the exhaust of a BMW <grin>) the fuel economy will drop like a rock !

Cheers
DD