Runs better because you changed oil brands? C'mon that's placebo effect...

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May 31, 2002
St. Charles County, Missouri
OK-- I asked the question on the "dumped my castrol" thread. It's my contention that most of this "car runs better since I changed my oil" business is simply placebo effect pure and simple. A 1-2% change because of weight change or going from dino to synthetic simply isn't enough to feel in the seat of your pants. Same with improvements after oil changes.

Agree or (I'm sure most of you will) disagree. Let me have it.
I disagree, I think that you can definitely notice a slight difference in the behavior of your engine if you're well in tune with it. I definitely noticed changes in my Firebird with the switch from Maxlife to Schaeffer Oil, and from Schaeffer Oil to GC. I also noticed a nice difference each time I ran Auto-rx in it.

For me, I notice mostly better throttle response in the midrange and low end, along with a smoother running engine overall.

With my wife's Honda, I definitely noticed it's quieter and smoother on GC compared to Royal Purple. And the valvetrain is quieter too.

I don't pretend to think that I'm gaining any horsepower from different oils, but there is definitely a tangible effect in throttle response from the changes.
Some people are more sensitive to their surroundings then others.
I tend to notice alot, regardless of what people say can/cannot be felt.
Use all your senses. Ignore the worthless psycho-babble.
I notice a difference after every oil change; same brand/viscosity. Jumping brands, viscosities, or dino/synthetic, typically gives a greater 'feeling'. This doesn't last long... maybe 100-200 km. I would say it is not a placebo effect. Is it measureable? Probably. Just my $.02
Your car also runs better and quieter after taking it to the car wash! LOL

I am a believer that one can sense a different sound and engine response betwen certain oils. No doubt. Gas mileage can change between oils, so why not be able to sense what the engine is gaining/losing? You can IMO
How can your car NOT??? run better with all that fresh clean oil...

I did notice my engine SEEMS! quieter with thicker oil...!?!?
I can tell the difference in my wifes RX/7 rotory after I change the oil, It actually will tell me when it is time to change! It tends to delute the oil so when it gets a little thin it will not pull a hill near my house in 5th! But with fresh oil it will pull it fine, and just sounds sronger and smoother!

I know this is a little different critter!!

I guess all oil is the same then. 5 year oil Valvoline or fresh new GC, same thing.

Originally posted by mrhonda:
I notice a difference after every oil change; same brand/viscosity. Jumping brands, viscosities, or dino/synthetic, typically gives a greater 'feeling'. This doesn't last long... maybe 100-200 km. I would say it is not a placebo effect. Is it measureable? Probably. Just my $.02

I'll go along with that.

Unless there was something terribly "wrong" or "incorrect" with a particular oil, I have difficulty believing that a new oil with a given viscosity at operating temperature is going to give any substantive, noticable improvement in performance over another brand of new oil with the same viscosity at the same operating temperature. Isn't another term for the phenomenon "self-fulfilling prophecy."
To some extent I actually agree with you.

I especially have never encountered a car running better after new oil, although I suppose IT could happen if the new oil helps better ring seal...

Now as for noise, in many cars I can definitely HEAR engine noises differently depending on oil brand and vis....
Some cars you can feel. Some you can't. I don't drive my parents cars or my GF's car very often. But I do change their oil. Never noticed a lick of difference before and after.

On my own vehicles there is a HUGE difference. Running too thin of an oil or too thick give different resaults as does the "shear down" effect of some oils. RP and M1 5w-30 actually "feel" thinner after 5,000 miles. My engine gets louder with thin oils at operating temp. Fresh oil always seems to quiet it down as well as making acceleration much smoother. Synthetic always seems smoother than dino. Power and mileage always stay the same, its the sound and feel of the engine that changes.
In the 80's my college car was a '79 Diesel Rabbit. I could immediately notice a difference in the sound and smoothness of the engine after an oil change (same weight and brand). I alway ran Mobil 1 (I don't remember what weight) and an OEM Volkswagen filter.

I think I changed the oil every 3K too
I've never noticed a difference in performance after changing the oil or after switching oil brands. But the sound does change even when sticking with the same oil. And yes, my Audi sounds like sack of nails with M1 0W-40, while it was nice and quiet with the blasted Castrol 5W-50. Go figure...
Good post, I've been thinking the same lately.
I agree with you. IMO, it's a viscosity related issue. Terry has stated before, the reason why M1 sounds louder in some cars is bc it's on the thin side. A GC is almost a 40wt oil, so yes, it will quiet down the engine a bit. I also think an oil with a good dose of FM's will reduce noise. Overall though, your absolutely right and that most of it is in your head. The only oil ever to make a noticeable difference in my car was RL and I believe it's due to the low Cf.
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