The bottle is labeled:

"The Complete Fuel Treatment"
"Hi-Performance Lucas Upper Cylinder Lubricant with Injector Cleaners and Fuel Conditioners"
"Neutralizes Poor Quality Fuel"
"Fuel Saver - Increases MPG - Gas or Diesel"
"Lubricates compression rings for easier pistion travel, more power and less cylinder wear."
"Contains special clean burning additives to facilitate a complete combustion burn for more power, more fuel economy and fewer emsissions."
"Creates a cushion seal at the valve seat for higher compression, more fuel economy and less valve wear."
"This product should more than pay for itself in fuel savings alone!"

Here is the story. Most of you already know much of it. I have a Jaguar S-type I bought about 1.5 years ago. It had 75k miles when I bought it. It now has about 105k miles on it. About 20-25k miles ago, the Check Engine Light (CEL) started coming on and staying on. When I checked it, it always said the right CAT was not working up to par.

I checked the O2 sensors on both sides and they were the same. I actually swapped them, one by one, right to left, to be certain the sensors were not going bad.

I tried Seafoam, MMO and RXP. The only one of these that would shut the CEL off was the RXP but on the next tank if I did not put another bottle in (@ $7-8 a bottle) the CEL would come back on.

A new CAT from Jaguar costs right at $1000 each and they will only change both at the same time, with labor costs at ~$1000. Unfortunately, I do not have that kind of green hanging out of my pockets (or any where) right now. I found some after-markets online for about $300 each, but there are no mechanics in town that will work on the Jag... I can do it myself (I think) as they are not welded on. But I have not had time and really do not want to spend $600 on CATs to find that it does not solve the problem. There are a number of things that can cause this OBDII code. That includes a cylinder not burning fuel completely.

So I bought new coils and plugs and took the intake manifold off and replaced all of them. Cleaned the fuel injectors while I was under there and replaced the PVC valve which is buried under there too. It ran a lot better after all that, but the CEL still came on with the same code.

So as a last ditch effort, I bought this 32oz bottle of Lucas Upper Cylinder Lubricant. It cost $10 at Wal-Mart and will treat about 100 gallons. That translates into about 6-7 tanks in this car or about $1.70 per tank.

Well, any way. After about half a tank ran through, the CEL went off. I thought, "Well I've seen that before. So I am not going to get too excited." Then I emptied that tank, and fueled again. I forgot to put it in the second tank and the CEL remained off. On the third tank I added it again and every tank since. I am on the fifth or sixth tank now and still no CEL! Normally, before this additive, if I reset the light, it will be back on with 20-30 miles (50 max).

I do not know what will happen when/if I stop adding the Lucas. I think I will run through this bottle keeping an eye on gas mileage. So far, the MPG have jumped from 19-20.5mpg over many tanks (which I always felt was low for this car) to 25-26mpg in city driving. That is over a 20% increase.

When this bottle is finished, another 2-3 tanks from now, I'll try running without it and see what happens.

I really had always thought this stuff must be 'sssssnake oil' when I looked at it on Walmarts shelf. Now I am not so certain. So far so good.

P.S. Based on Lucas' calms of neutralizing poor quality fuel, I decided to try it with 89 octane gas and the car runs beautifully. I have been using regular gas in the last 3 tanks with the Lucas additive. There is no knocking, pinging or any strange engine sounds and the car seems to have more power than ever... MPGs have remained up there in the 25-26mpg range too.

I'll let you know what happens after a couple of tanks without it. It may have just cleaned up a valve seat that the other additives did not... But I ran a lot of tanks of them through too hoping for this result.

(No. I do not work for Lucas! But their product is working for me...)

 

A handful of gasoline additives are great products that actually do clean the fuel injection system. Chevron's Techron Fuel System Concentrate is one of them. I pour a 20-ounce bottle of Techron into our S-Type's fuel tank every time I do an oil & filter change (6,000-mile intervals on this car using Castrol 5W-30 conventional oil). Perhaps this Lucas stuff is a great product as well. You seem to be getting positive results from it. I would stay with it until you don't anymore. These S-Type fuel injectors have tiny orifices and tend to clog rather easily. Sometimes a good fuel injector cleaning is exactly what you need to help with misfires and turn off the check engine light....

 

Any update. Is the CEL still off? Are you still using the additive?

 

You say CAT not working correctly; what diag code(s) do you get? Is your Jag 2005.5MY or earlier? If so there are two (2) O2 sensors on each bank, pre CAT and post CAT. The primary O2 does most of the work but on occasions the secondary O2 does go out. Have you checked that one by changing it over?

If later this does not apply so disregard.

 

My XJ6 had LUCAS fuel (petrol) injection equipment, the mass air flow sensor (hot-wire) was LUCAS I know 'cause I cleaned it myself. The car ran on gas/lpg all the time, even on start-up from cold. After a year of running like this, the car ran badly on petrol but perfect on gas. Problem? Clogged petrol injectors! So...it wouldn't exactly surprize me that LUCAS fuel cleaner/injector cleaner does the trick, does what it says on the tin in fact. I understand that clogged injectors for both petrol and diesel engines are a very common fault. Also I understand that any computer-based device telling you something is not necessarily to be believed. It's only a "stock" guess from a look-up table and calculation from sensors. Can't beat a mechanic's experience and a mechanic's ear.
Leedsman.
N.B. I think it's called, "Lucas-CAV"., a british company, been going 50 years to my knowledge.

 

RGB - it's an earlier car and if you read his posts you'll see he did all sorts of work on it including swapping O2s.

 

My bad, I thought he changed the upper O2 sensors with each other not the lower (post CAT) ones. Again, I will say its a very long shot that those would fail.

 

Guys

After reading this post i poured Lucas into my tank. It did not take the CEL off.I live in CA, car is V8, 2000S. I was getting the same code P0420 all the time. have tried swapping the sensors one at a time, and checking the o2 curves through my obd-2.In my case lucas did not help. I went to a local muffler shop, and he charged me 300/- and replaced the rh cat, with AIRTEX cat, legal in CA. Bravo, CEL is gone for the last month.02 graphs are good.

before i forget, checked the removed original cat, the honeycomb was melted.

i went to a local jag shop, he wanted to check 02 sensor grounds and all that crap.by swapping the sensors you have confirmed the ground are good.THis is dishing out more greens.my wife is happy as she does not face that blooming CEL light anymore.

 

Can someone explain how the O2 graphs can be good if the cat is melted and not working thus overall causing P0420? More than strange.

 

I think he said the graphs were good AFTER changing the cat.No mention of readings with bad cat.

 

hmm, have re-read it and it's soooo unclear

The real question would be.... what melted a cat?
Likely answer - misfires i.e. unburnt fuel which then burns in the cat.
And then you hunt the misfires
But no comment on that

 

Yes, it was very unclear. A little more detail sure would help in understanding the before and after results.

 

Guys, maybe i was one over the bubly limit when i typed in the thread.

1. Lucas did not do the job for me.I was getting P0420(RH), the o2 graphs were similar for fwd and aft o2 sensors, meaning cat is not doing the job.
2. to take o2 sensors out of the equation, swapped LH and RH sensors, and the graph were the same for RH side.
3.After changing RH cat for 300/-, o2 graphs were good.i hope i have answered your querries? i u need more info glad to help