OK, so I changed my o2 sensors a couple weeks ago. Before that, the truck was running very rich. So much so that you could smell the excess fuel just standing near the exhaust. After changing the o2's, that smell went away, only to be replaced by the slight smell of burning oil. Tuesday, I changed the oil in the truck. While draining the old oil, the oil sitting in the top of my drain pan had a dark foam sitting on top. The foam was the same color as the oil. The only thing I did different this oil change was use the K&N HP-3001 filter instead of the HP-2004 and a quart of Lucas Synthetic Oil Stabilizer in place of one of the quarts of Mobil 1 5w-30 Synthetic. After the oil change, there seems to be a strong smell of oil burning. I have not been able to track down any significant leaks as yet, but I haven't been able to look at the underside since I've noticed this. I need some help with this, and thanks in advance for the help.

 

Need to get under and check for leaks. Lucas shouldn't foam, but if it is the only difference you had....

If you were running way rich, it may have gotten some fuel in the oil which made it leak. Just a possibility. Track down the source of the smell. Not sure what else to tell you..

 

Well the Lucas wasn't used in the previous oil change that I did, just straight Mobil 1 5w-30 synthetic. I remember seeing foam in the oil mentioned somewhere, but not sure what the cause or fix for it was. The truck seems to be running OK, idles smooth, accelerates with ease, just the normal minor Rover leaks and that burning oil smell. I'm stumped.

 

Ok, so you used Lucas in the oil 2 oil changes ago?
The last time you used the oil drain pan was also the last time that you used Lucas in the oil?

 

No, I have never used Lucas oil additive prior to the oil change that I just completed this past Tuesday. I added it to the new oil that I put in. The old oil that I drained out was straight 5w-30. No additives. This oil change that I just completed is only the second oil change I've done since I bought the truck in September.

 

This is just a personal preference, but 5w-30 is too thin for my taste. I don't trust it. I don't trust full synthetic either, but I don't have any real reason for that, other than just not knowing enough about it to justify trusting it.

Does it seem to be losing any oil, like it's burning it? You getting any oil on the spark plugs?

 

I have not pulled the plugs to inspect them, so don't know on that one. It is not losing significant amounts of oil. There's no puddle in the driveway where I always park. The drivers side o2 did have some oil on it when I changed it, so there is a small leak near there, just not sure where.

 

Need to wash up your engine and find where it is coming from. There is nothing wrong with your weight or type of oil. Full synthetic has a stronger film strength, so you can run lighter oil. Mobile 1 isn't the best, but it is good oil. I run 5W30 in mine and I have 168K...If you run thicker, and you have build up in your passages, it will restrict flow and you won't get the protection you need.

 

5w-30 is only good upto 95*F, it does not have the heat resistance of a Xw-40 which is good upto 120*F.
A full synthetic will not break down from heat as fast as a dino oil will so while a 5w-30 full syn holds up in the summer a 5w-30 dino oil will not.
Engine sludge is caused by oil breakdown, oil breaks down from heat, you can change your oil every 1,000 miles and still get oil sludge if you use the wrong grade of oil for the application.
The oil itself does not break down, it is the oil additives that do, the bigger the viscosity range the more additives the oil has.
Motor oil has a infinite life span, take dirty motor oil and distill it and you have clean fresh base stock again, dump in your additives and BAM!, brand new motor oil.
There is zero difference is virgin stock and recycled stock motor oil, it is all in the additives.
The place that I worked for, the place where I sold engine coolant also recycled oil and that was one of the things that I had to learn, how motor oil is made.
It is all in the additives.