96 V8 with 50k on it Gunked up ... why?

Stop and go driving, water/coolant leak, poor crankcase ventilation (PCV system)

I have used Pennzoil in my '96 Explorer since brand new, now has

125,000 miles >I had to replace a leaking valve cover on my 96 this weekend, and was

Back when I used Pennzoil and Quaker State (in the 1970s admittedly a long time ago), I had this problem. I switched to Havoline and then to Mobil 1 and have had no sludge problems since.

I know that in the 70's Pennzoil had a lot of parafin in it. Had problems with both Havoline and Pennzoil - saw quite a few engines sludged by both. I assumed that oil manufacturers had decreased parafin content because of the

195 degree thermostats - not good for parafin. Read something recently about oils now being grade 2 basestock to deal with the higher engine temperatures.

My first thought would be short trip driving where the engine cannot fully warm up to burn off the condensation in the engine.

You might think about running a can of Gunk engine flush thru it at your next scheduled oil change. Or Seafoam. Clean it out then switch to Mobil1.

Maybe someone who is more up on oil will chime in and have a definite word on parafin.

I'd vote for other factors. In years gone by I would not touch either Pennzoil or Quaker State, but I don't think they are much different than other oils that meet the API ratings these days. 302 V-8 are not noted for sludge and I am sure there are many Explorer owners with V-8s running Pennzoil.

I'd suggest you have someone check for excessive blow-by. There is a good chance your compression rings are not seating properly and therefore your engine is experiencing excessive blow-by into the crankcase which is contributing to the sludge. If is also possible your engine might have a hot spot because of poor water flow to the heads - not sure how you can check for this.

Ed

"ross via CarKB.com" wrote in news:5552d4556e390@uwe:

First off, let me say that I know a fair bit about hydrocarbon chemistry but nothing special about motor oil design or production.

That said, I can comfortably say that reasonable engine heat and paraffin base stocks are not a problem.

There are several common and technical uses of the word "paraffin." In the oil business, a paraffin hydrocarbon is simply a saturated (single carbon bonds) organic molecule with a generic formula of CnH2n+2. The value of "n" can range from 1 (methane - the princpal component of natural gas) to "a large number."

When you get into long hydrocarbon molecules (big values of "n") the melting point can get fairly high. Candle wax (commonly called paraffin) is a good example of these long chains.

Typically, motor oils will not have the long hydrocarbon molecules present since they have low boiling points and are "cut" out by the refining process. Either way, reducing the "wax" content of an oil will help with controlling viscosity behavior of the oil at various temperatures.

As other posters have noted, there are several possible causes of sludge formation in an engine. Paraffin content is probably not one of them.

Check the thermostat, make sure the engine heats up when first driven for the day. Check blow-by and PCV. Check the air intake system. Check that oil is circulating properly through the lifters and pushrods.

i read in consumer reports a few years ago that all oils with the "approved for gasoline engines" starburst symbol were essentially the same except for the weight.

Why did you have to rebuild the engine, how many miles did it go before the rebuild, and was it sludged up at the time it was rebuilt? If the engine was not sludged up when it was rebuilt, I think the blow by idea may be a good one. If it was sludged when rebuilt, I think other factors would be at fault.