I am looking to maintain a well conditioned 87 XJ6 engine that I recently purchased. I would like to get at least 3 more good years (without any major repairs) on the engine before either doing a rebuild or swap. In any case, I would like to get some feedback on K&N air filters from anyone with a Series III. With fuel prices increasing every day, is there any improvement on gas milage & engine performance?

Other suggestions are welcome. Thank you in advance.

 

I'm sure somebody somewhere has used one, but don't expect to see any measurable real world improvements in economy or performance.

 

Yup.

I had one on my Ser III for years. No improvement in fuel economy and maybe, just maybe, a slight increase in upper-rpm horsepower....and that may have simply been me wanting to feel more power to justify the expense of the filter :-)

Still, though, there's the advantage of a K&N being the last air filter you'll ever buy for the car.

Cheers
DD

 

If the engine is in good shape now it'll probably soldier on for much more than 3 years. A head gasket replacement might be in your future, though, if it hasn't already been replaced. Pretty common on the old 4.2s.

As for fuel economy just make sure your ignition system is in good shape...including a functional vacuum advance...and that your timing is set to the 17ºBTDC spec.

Fuel mixture can really hurt economy as well. A shop with an exhaust analyzer can tell you if you have a mixture problem and, if you do, we can help sort it out. Of course, a major mixture problem is easy to spot: black smoke, black spark plugs, strong exhaust odor.

If the engine is well worn with low compression it'll never give optimal fuel economy....which isn't all that great on these cars to begin with. It's just isn't a terribly fuel-efficient engine and it's lugging around 4100 pounds of automobile.

What kind of economy are you getting? Driven gently you should get 12-13 mpg in city driving and about 20 mpg on the open road.

Cheers
DD

 

Thanks for the replies so far.

Doug, my fuel economy is about 19 or 20 on the highway so thats a good thing. The engine has a little over 98,000 miles so I haven't noticed any of the possible engine issues you mentioned just yet (knock on wood). I do feel that the horsepower should be a little better which could be the timing being a bit off. I plan to have a tuneup done very shortly. The ignition turns over nice and handles well past 70 mph. I have located a local mechanic that specializes in older model Jags so I'll talk to him about your suggestions.

Thanks again!