I bought my t/a with 69k on it, made no noises, no knocking, I put mobil 1 in a little after 70k, and now I can hear knocking, which is I would assume is piston slap, now I don't understand whats so good about synthetic, I mean regular motor oil goes into cars that will last well over 140k, I don't see why spending so much more money for synthetic is worth it when it makes noises more apparent? I've been using mobil 1, I just picked up castrol high mileage 10w40 and I'm going to see how that is on noise, but my main point behind this post is can you see an adverse effects from switching to regular motor oil after using synthetic for about 3k, I'm pretty sure the whole life of my motor had reg dino oil in it. I'm willing to stay with synthetic if you guys can explain to me why I should keep using it, but really im curious to see if the regular motor oil makes the noises go away, and if it doesnt I would probably go back to synthetic, is it a bad idea to keep switching like that?

 

synthetic just has more additives in it so you don't have to change it as often under normal driving conditions. I've never heard on any adverse affects with one versus the other.

 

Amsoil is probably the best and oldest 100% pure synthetic oil on the market. They advertised you didn't have to change their oil until 20k miles back in 1970! Go to their site and read what they have to say and then you can make the right decision for your situation. I switched from regular Mobile 1 to extended drive Syntech to help protect my motor more. Synthetic oils do outperform regular oil in wear protection, sludge, and burning. Just go to Amsoil and read what they say...ok.

The Duke

 

Mobile one made my piston slap louder. Red line made it quieter.

 

yea i think mobil 1 sucks, i'll never use it again, but i think i'll be going back to regular oil, just change it like every 2k miles, i have access to a lift so it takes like 5min to change oil.

 

I recently replaced my 02 SS with another 02 SS. I remarked how the new car's engine was so much quieter than the old one. Then I put a fresh load of Mobil 1 and I noticed it got noticeably louder. Nothing to worry about, but it did make me wonder. I think I'm going to try Amzoil or Royal Purple next year.

 

For daily driving, the WalMart 10w-30 dino and the WalMart filter does great.

 

I switched from dino (original owner was using Pennzoil 5W30) to Castrol semi-synthetic 5W30 at 50K miles with no increase in valvetrain noise, piston slap, or consumption. I've put about 6K miles on this car since May 2004 and the car has never used any oil between 3000 mile oil changes. Having said this, the passenger side valve train has always been noisy and the tensioner makes a clicking sound which I need to address.
I assume you mean "knocking" on startup only which is probably the pistons.

 

wow that sucked, i took out the mobil 1 and put in regular oil, and it made the knocking noise 2x louder, which I'm sure isn't piston slap now, it sounds like its coming from up top, what could be causing this? I'm thinking a lifter, but what would a loose rocker sound like? I'm real pissed that I just drained out the mobil 1 with only like 300 miles on it and put in a regular oil which made the noise louder..wtf? I have real good oil pressure so I would rule out bearings or anything like that.

 

You could switch back and forth between oils every week and it would not harm your motor. That said, it begs the question of why anyone would wish to do that.

Without a more detailed description of your engine noises I guess we could go forward with the presumption that it is piston slap you are hearing. Naturally, you would want to ensure that is all it is.

Whether the oil is petro or synthetic is not relevant to your engine noise. Oil weight is relevant.

You didn't mention what weight of Mobil 1 you used. From the (constant) comments here it is understood that Mobil 1 is on the thin side of whatever weight is listed. Heavier weight oil will provide a better "cushion" and mitigate your engine noises. So, use a heavier weight of Mobil 1 or any other chosen oil brand. Just don't go overboard with that thought. Your LS1 will not keel over and die if you use something other than 5w-30 or 10w-30 as is listed in your owners manual. ANY decent oil of a reasonable weight will work, but a hard working motor wants a heavier oil and an easy working motor can use a thinner oil.

As to the question of petro vs synthetic, the choice is up to you and your wallet. The facts are indisputable, however, that synthetic oil is a better quality lubricant than is petroleum oil. Synthetic oil needs FEWER additives, not more, to maintain its weight rating, leaving more oil and less additive in a given bottle.

Synthetic oils oxidize less, have less ash, have less evaporation of volatiles, produce less sludge and varnish, are naturally detergent, and offer better lubricity. These are proven facts you can look up anywhere on the web.

They are more expensive for all these wonderful attributes, but many folks don't mind. You can lessen the blow by keeping the oil in the crankcase longer between changes. This is safe and effective, regardless of what you may hear from the "change at 2k miles" crowd.

 

Thanks, good input, anyway im sure it isnt piston slap, its definatly a tap, from the valvetrain, I'm leaning towards a rocker or pushrod, i heard that pushrods bend real easy on these motors?

 

only if you go from 3rd to 2nd in a 6M never heard of it in an A4....But yes, they can/do bend if you over-rev it (i.e. miss a gear, not jsut hit the rev limiter)