Well here is the story, my 111,000 mile 92 F150 with the 4.9l engine runs amazing, but I recently changed my oil and accidentally bought Valvoline Max life 10w 40 synthetic blend instead of the normal I usually buy. I normally run Val Max life 10w 30 in the normal oil. I did notice that I lost about a quart over 4k miles on the normal oil before changing it 2 days ago. Well i put the new oil and filter in yesterday and noticed a small drip when the car sits for over an hour. Not big at all. i Got under there and it is either coming from the drain plug, or near the rear main seal is a little wet. Could switching to a heavier weight and an= synthetic blend cause this? It might have been leaking a little before the switch I am not sure. Also would you reccommend draining the oil and putting the normal dino oil abck in? Will that slow or stop the leak? Thanks

 

A synthetic blend could cause it to leak. The rule of thumb is that if an engine leaks or burns dino oil, it will leak or burn more with synthetic.
If it were me, I would drain the oil out and put the right oil in. 40 weight is too thick.

 

Howdy,

Shouldn't have caused a leak, but I'd just go back to the normal oil you have always been using at the next oil change. Prolly time for a new drain plug too.

Adrianspeeder

 

Yeah, Synthetic oil is known for leaking when you put it in a high mileage engine. Something to do with it having smaller molecules that sneak by older, worn-out seals.

 

is 10w 40 too thick? I am in Texas where the temps reach over 100. I thought you were supposed to use thicker oil in summer in hot climates.

 

10W-40 will be fine. Some might object, but I would even consider 15W-40 or 20W-50.

 

I had the same experience with Ch_vy (sorry for the swear)

It started leaking about a week after I switched to synthetic.

I think that dyno oil leaves deposits no matter how good of stuff you use. Then the synthetic cleans them out and your gaskets leak. For me, it was the valve covers. I intended to replace the gaskets thinking that would solve my problem, but they were in good shape (and made of rubber anyway). I cleaned everything up, re-installed the valve covers and never had another problem.

To be honest, I'm not sure it's worth the effort. Dyno oil is pretty good stuff nowdays.

My 2 cents

JW

 

Most oil marketed as "100% pure synthetic" is highly refined dino oil. I think Castrol started it, and Mobil jumped their $#!+ about it; now Mobil does the same thing.

 

Yea, but does it matter?

Correct me if I'm wrong, but all "Synthetic" is, is (a) a consistent & limited mix of lubricating hydrocarbons without all the parrafins, creasote & other trash that is normally included in dino oil because it's too expensive to refine it out and (b) synthetic used to be only achieveable through chemical reconstruction in a test tube. Dino oil has the same optimum hydrocarbons as synthetic, it just has more of the other crap that gums up lifters & rings. Synthetic is more consistent & is lacking the crap that refining used to be unable to remove. If refining of crude is now sufficiently complete to be able to end up with the same consistent hydro mix (+ the additive package), then what difference does it make? A C10H12 molecule is the same whether mother nature made it, or a chemist.

IMO synthetic is nearly always best - it excludes the gumming crap.

 

Well, you could ask the same question about anything. Does it matter if a seller tells the truth about what he's selling?



If dino oil can now be refined THAT well, why not say "Hey, we've figured out how to refine natural petroleum to the point that it's as good/better than synthetic!"



Aaaaaahh... But then, they would have a harder time charging as much for it as people were willing to pay for REAL synthetic! So by lying to us, they boost their profits!

So you tell me: does it matter?

 

Well, your response is provocative, but not terribly informative. Perhaps the question was not stated properly.

Your reply seems to indicate that it costs no more to produce a so-called "synthetic" through hydroprocessing than it does to produce a "dino" Class III conventional motor oil and so they should cost the same. Based on the chemical processing equipment and processing involved, I find that difficult to believe. Does it cost as much to produce "true synthetics" by building PAO's from scratch, as it does to make a hydroprocessed faux synthetic? I can't say, perhaps you or others on this forum can?

The question is, is there any impirical evidence (or based on your personal experience) to indicate that a lubricant derived from PAO/Ester chemical construction process is markedly better than one derived from the hydroisomerization/cracking/reforming of base mineral oil, assuming no difference in the additive package?

And if so, are there any products on the market now still made from the original "synthetic" manufacturing process using the construction of PAO/Ester base oil from simpler molecules? I'd really like to know that. Amsoil maybe?

And finally, is there sufficient advantage in your experience to justify the cost of synthetic-blends, true PAO synthetics, refined synthetics vs ordinary cheap "dino" oil?

 

Use as many big words as you like - I've studied chemistry, physics, & engineering, too.

It's all MOOT.

The point is: if they're selling something that's NOT what they say it is, they're lying. That was the point of my original post, and that was my only goal.

If you want to debate PAOs, additives, & isomerization, go check out BITOG or find darkdan here or on CVN.