Does anybody on here run this both with the oil and with the fuel

 

Yes. Have been running it in both in all my vehicles for many years!

 

how much do you add to each? I'm about due for my first Oil change in the XJ

 

I can't suggest how much for "you" to use, but I will say that "I" use a quart every oil change and about 8 oz every fill up.

 

never heard of this stuff, would anyone like to enlighten me?

 

Supposed to improve mpg and help extend/improve engine life and performance

 

Every fill up!! That must get expensive!! Is there a noticeable difference?

 

It runs me about $.50 per fill up. I buy it online for about $2 a quart. And I have been using it for over 25 years. I believe it does make a difference, especially with today's ethanol fuels!

 

I run it in my gas tank and I think It makes a difference. My odometer is k.o. right now so I can't get a for sure answer. But I try and combo it with good gas and not fill up at el cheapo gas stations. I haven't mixed it with the oil yet because I'm not due for a change yet. And like JCKustoms said it is like .50 a fill up. But to me, the extra few cents are worth it to keep my baby alive and well

 

While this stuff has been around for a VERY long time, I'd use caution adding this to your oil. It has a quality of removing sludge not unlike a flushing solvent and that's what many use it for. The down side is what happened to me when I used it on a Mopar 318 in a police cruiser I was restoring two years ago.

I had used it and drained out the oil/Marvel mix after some miles. As the car was both a retired copcar and had at least one owner after, I knew that the motor needed some TLC. This was part of what I did to get it back into better shape. After draining the used mix, I added fresh oil and a new filter and headed for Chicago from here in Western Pennsylvania to a car meet. On the way back home, I lost oil pressure on I-80 in Indiana. The car made it home, though my stress level for the remainder of a long trip wasn't pleasant. The engine suffered no damage miraculously. I wouldn't recommend doing this.

Bottom line was that the Marvel kicked loose enough crud that didn't leave with the drained oil/Marvel mix that it clogged the new oil filter. I'm sure many have used it without ill effects, but I'm also sure that I'm not the first that has suffered this type of situation by using such a product. Just be careful with additives like this.

FYI, I'm partial to Lucas.

 

Used to work in a body shop back home in NC. We had a '68 Camaro with a 327 and a 2 speed Powerglide tranny. It sat for 12 years with the hood up and no cover over the open intake. One day, the boss, a retired WWII vet, wanted to see if we could get it going. So we cut down the tree that was growing up through the engine bay and pulled it to the shop. Drained the crankcase, pulled the plugs. Tried to spin the motor, of course that didnt happen. So we blew what water we could out of the cylinders. Pulled the valve covers and poured in some Mystery Oil onto the valvetrain and into each of the cylinders and let it set for a week. Put a breaker bar on the crank bolt and was able to work the motor loose enough to where the starter would turn it. We kept that up for another 3 days, fill the cylinders and spin the motor. We changed the filter, added a carb, installed new plugs, wires cap, rotor and pick up. Put some go juice to the carb and she fired right up. Smoked for a while but she ran great!

 

Thats awesome, AWESOME car too!
where is it now?

 

Ok, that's not bad. I expected it to be way more then that. Where is the website that you get it for $2 a quart?

 

I buy it in 5 gallon tubs. That's the only way you'll get it for around $2 a quart. I also buy it through my business so I'm not sure if you'll be able to purchase it, but I'll get you the web address anyway.

 

I used it when rebuilding the engine on a 2.0l Ford Contour for my daughter that had been mistreated and sat with the head loose and valve cover off in the Alaskan climate for over 6 winter months. Before I got it all back together, I looked down the spark plug holes to see enough black gunk buildup to shake your faith in religion. So I poured a cupful of MMO into each cyclinder hole and let it set for a weekend. Finished the timing belt, added the plugs and she fired up like new. Took half an hour to blow all the gunk out (I also had Seafoam in the gas) but that lil' 2.0 is still chugging like a brand new gal over a year and half later.