"WHY" Does Old Oil Slow Engines..?

[solaris=amazing]

Hey guys, i seriously notice on my car now rather then smaller engine cars i had in the past. I have a 95 ford tbird with a 4.6 V8 that has just over 133k on the ticker. As soon as i get past 2000 miles, after a good oil change, it seems as if i lose atleast 15-25 hp...especially torque.

Example, after a oil change, i can go WOT from a stop and get a good 2 second chirp (no smoke)....after 2000 miles or so, i punch it...nothing.. Just a slow windup.

Is it that the oil gets thinner and loses it's lubricity..? But why would that hinder HP and TQ..? BTW, i do use 4 qt's 10W30 castrol and 1 qt Lucas Oil Stabilizer...works good.

BTW, does it have something to do with compression..?

[beyondloadedSE]

Oil breaks down and loses its weight iirc. Like if its a 5W30, it will go completely to a 5 weight or a 30 weight. Not sure which direction it goes. Maybe somebody will chime in.

Anyways, thats the whole purpose of synthetic. It doesnt do that.

[woofhaven]

10W30 oil is 10W weight oil, with polymer additives to make it behave like 30 weight oil at 100 degrees C. When the oil undergoes thermal breakdown, two things can occur. One is the breakdown of the polymers, so that the oil always behaves like 10W weight oil. The other is thermal breakdown of the base 10W weight oil itself, resulting in an even thinner oil. Bottom line -- thermal breakdown = thinner oil.

None of this should be happening to an appreciable extent in 2000 miles after an oil change. You've got something funky going on. I would try running you car without the Lucas additive and see what happens. Some research has shown that oil additives (including Lucas) can have unpredictable results when they combine with the engine oil.

[woofhaven]

That car doesn't have hydraulic lifters, does it?

[solaris=amazing]

Hydraulic lifters..? I'm not sure..it's a 4.6 281ci SOHC...that's all i really know..i'm not an engine man..lol..

Well, to be honest with you..i drive hard. I know that's not good, it adds wear and tear, but it happens. Rough=smoking tires sometimes, flooring it, 100mph+ almost daily.

[mturner1]

Well, I wouldn't think that castrol would be breaking down after 2000 miles...I suspect you may have an incompatibility with the Lucas Oil....It sounds like the viscosity enhancers in the Lucas oil are causing a substantial increase in your oil viscosity...if you have an oil pressure guage, I would think you may see this as a pressure increase due to the viscosity increase. You may want to try one of Amsoil's brands of XLmotor oil....to start. Check out the guy's website from which I purchase my oil. www.lubedealer.com/jtubbs

[public]

No lifters on an OHC engine. Lifters are for pushrods.

[woofhaven]

I'm with mturner1. Even with the way you describe your driving, you should not be getting breakdown that quickly. Try good oil without additives and see what happens.

[ec437]

2 second chirp with no smoke? Try timing it with a stop watch. I think 2 seconds is a little long for a "chirp".