Do you perceive engines running better after oil changes?

[woods]

Here is something funny for ya. Back a zillion years ago when they would strip a Harley down to almost nothing and make a hill climber out of it. To get the last little bit of oomph out of it...They would fire it up with fresh oil in it, let it run for a few minutes, kill it, drain the oil and run the hill. They would do the same thing for the next run.

[ta TACO]

So, what does this do? I can't think of anything positive that could come of it

Davin.

[Brokenarrow]

So, what does this do? I can't think of anything positive that could come of it

Davin.

Sounds crazy, huh? I'd imagine the engine would lose a small amount of internal "drag" from the oil-pump, plus lose a few pounds by draining the oil. I wouldn't reccomend trying this with your drag car

[woods]

It was all about internal drag. We do it to a much lesser extent these days with Harley drag bikes. Since Harley uses a dry sump system (that does not dry very good) we increase the amount of oil the pump can pull from the case and lessen the amount going in. Just enough oil to make it survive. The idea here is...have a foot race with someone, have him run in a foot of water and you on dry ground.

[Whateverman]

the only difference i've noticed after an oil change is that the oil these days is runnier than water,i end up dumping lucas oil in everything hoping that there will be at least something in there lubricating things
after the last oil change in my f250 ( 6.9 diesel) the dirty old beast has lost nearly all oil pressure below 1000rpm,it may be totally old ,fragged and worn out but i just can't believe the difference
the craziest thing is when i can't find diesel rated oil (15w40) and have to dump some regular old car oil (usually 10w30) in it the pressure improves...until the cornbinder burns it all or leaks it out of course....

[averagef250]

I should've said no oil-flow Of course there is a few seconds worth of residual film, but I don't like to rely on a residual film of oil any more often than is necessary.

How many engines have been damaged by seconds or even several minutes without any oil in the engine sans a light film on the bearing surfaces? Probably none provided they weren't under a load.

When you have the engine loaded with no oil flow the oil in the bearings heats up to the point of failure, the crank journals contact the journal bearing surfaces and eventually there's a failure. At an idle under no load the engine bearings aren't under much stress at all, the oil film that's in there is plenty to form a wedge and support the crankshaft/rods.

Plain bearings don't need oil pressure to work, they just need oil in them. A plain bearing doesn't rely on pressure to keep the two elements from touching, the oil naturally forms a wedge that seperates the parts.

[fitzwell]

Robroy, perception becomes reality.

My old truck is so appreciative of ANY attention that I think he (yup, a male) just runs better as his way of saying "Thank You for showing me you still care.".

the ex used to swear that her truck ran better after she washed it..


As stated, older vehicles , maybe. Newer units, not so much, but the driver usually picks fuel economy on a fresh oil change.

[rjewkes]

i can vouch for both newer EFI/MFI and olderr 50's carb tech. My oil change on my truck can make it run quiter and smoother and certainly if it has to move its internals through correct thickness oil, it will feel more powerful then if it is moving through oil thats too thin.

also when i got the oil change in my 89 cougar efi v6 it ran smoother and felt more shure of itself than with the old oil.

[1972hiboy]

I cant say that mine runs any better after a oil change. like was stated earlier if the oil was the wrong viscosity or contaminated then switched out for the correct oil then it may improve . The regular oil changes are key to keeping that engine that runs so good running good for a long time. I had a buddy that had bought a mazda Miata to deliver pizzas with. he for some reason hated maint his car. finally with 20k he decided to bring it over my my place for a oil change. it was black and nasty but the car never really ran differant. There's my !

[Brokenarrow]

I should've said no oil-flow Of course there is a few seconds worth of residual film, but I don't like to rely on a residual film of oil any more often than is necessary.

How many engines have been damaged by seconds or even several minutes without any oil in the engine sans a light film on the bearing surfaces? Probably none provided they weren't under a load.

When you have the engine loaded with no oil flow the oil in the bearings heats up to the point of failure, the crank journals contact the journal bearing surfaces and eventually there's a failure. At an idle under no load the engine bearings aren't under much stress at all, the oil film that's in there is plenty to form a wedge and support the crankshaft/rods.

Plain bearings don't need oil pressure to work, they just need oil in them. A plain bearing doesn't rely on pressure to keep the two elements from touching, the oil naturally forms a wedge that seperates the parts.

This would hold true if all engines/clearances/oils were the same but they're not. So there are a lot of variables that can throw a kink into your theory. Reciprocating assembly slightly out of balance for one reason or another, excessive clearances due to wear, contaminated/broken down oil etc.etc. You ever start an old worn out 360 after an oil change and hear it clunk,clunk,clunk, for 3 or 4 seconds ?

[rjewkes]

in the cougar i actualy went my first two years without an oil change. when i checked it it was as clear as brand new oil. but since i was heading across state i had it and the filter changed, also it picked up about 3-4 mpg with the new filter and oil.

god bless its litle v6 gobs of power, and still gets 27.4 mpg highway sadly it drops to around 23-24 in town.