So i needed an oil change and when i went to the store the didnt have one quart of 5W-30 that i needed because the gallon one was shy of the 4 quarts i needed. so i asked the attendant and he told me to just use 10W-30 since itll be better for me. at first i didnt want to since i had an engine rebuild done 3k miles ago (about 8 months), but i needed to do it today since i am busy the rest of the week. so i got 5 quarts of it. went home drained my oil and only put 4 quarts(5th was for a minor leak if i ever needed it). my dad said i shouldnt be using thicker oil since it makes it knock because of something blah blah i dont know. he was right. now i hear a slapping noise maybe a knock. could it just be that the motor is not used to running through thicker oil? will it go away?
funny thing was my uncle put 10W-30 when he rebuilt it but i didnt know till he told me after a few oil changes. i'd just been using 5W-30 since then.

anyways... should i be worried now or is it something the car has to get used to? any help would be greatly appreciated thnks -Aaron

 

There is no such thing as a motor getting "used" to any oil. You were using 5W30 before with no knock - thats what to use again. Certain oil filters will cause a knock on start-up, but that should go away within a minute or less.

 

I've been using 10w30 for years.

 

Hmm then its weird. i also switched from fram filters to wix but that was just it. its weird that it knocks now. ill drive it around for awhile and see if it goes away and if not ill just take it to my local third gen mechanic and see what he says

 

throw 8 oz of marvel mystery oil in and i bet it goes away

 

theres not enough difference in viscosity between 10w30 and 5w30 to be an issue, you might have a defective oil filter?
are you getting oil pressure? any time you swap oil in an engine its best to refill the oil filter if its easily accessed, and verify the oil is at the correct level,on a chevy v8 thats usually a minimum of 5 quarts of oil, pre-filling the oil filter prevents the delay in oil reaching the bearings and moving parts, most guys know that if you fail to refill the oil filter theres a very brief time before the engine can re-pressurize the oil passages, that is usually not a problem as theres a protective oil film on the bearings and the loss of floww rarely lasts over 10 seconds.
BUT theres some chance its not rods or bearings or pistons making the noise, more than once Ive seen a burn rocker make a noise that sounded a great deal like a loose connecting rod bearing, you can burn a rocker ball in a few seconds with no oil flow, Id suggest adjusting the rockers and see if you find the source of the noise, Id also look at the oil pump pick-up, it might just be a coincidence, that the oil pump pick-ups come loose. whats your oil pressure gauge read?

http://forum.grumpysperformance.com/...php?f=54&t=117

 

Another suggestion is to run a good quality engine flush thru it. I've used Amsoil brand in the past with good results. A motor with a lot of oil sludge in it can make the sounds you're describing.

 

welcome to the forums

please note that the OP claims the engine was rebuilt 3k miles ago. Offering suggestions is great but they should have bearing to the problem at hand.

To the OP

running 1 quart low won't even cause a knock

mixing 10w 30 with 5w 30 won't cause harm so don't get all in a lather about that

you should put 5 QUARTS in at each oil change

the oil change is a coincidence.

what you have is a mechanical sound and you need to pinpoint it. You are there, we aren't. If it's from the lower end then I hope you have a warranty from the rebuilder

if it's top end, then try adjusting the rockers first and go from there

 

Alright. ill see about adjusting the top end and see if it helps. i didnt want to add too much oil since my autoshop teacher told us it causes oil foaming and i didnt wanna risk it. ill also try to pin where it comes from. to me it just sounds like a slapping noise but i dont know yet.
my pressure is good. reads around 75 when i turn on the car and when it warms up drops down to about 40 never really goes under 40.
now it not that noticeable but i can still hear it.
thanks for the help -Aaron

 

He's running a V6....

 

Last I checked, a gallon is = to 4 quarts

 

i told u to add about 8oz. of marvel mystery oil. it should quiet down the bottom end and if it is a lifter,it will stop it from tapping.it should clean your engine out too.

 

I rarely pay attention to the user profile, thus I did not see he has a sixer.

it's still a coincidence and not related