Why would an LS1 5.7L V8 get an Engine Knock after Switching to Synthetic?!?

Question

I bought my 2000 Z28 3 years ago, and It was in Beautiful Shape, both Cosmetically, and Mechanically.

After I tried to Pamper it, I think I am turning Gold into ****, now!! :(

The guy used Regular Pennsoil 10W-30 Motor Oil in it. It ran Great!! I changed it using the same oil. Ran Great!!

Then, I deside to Switch to Synthetic! I thought that would be a Good change, since I want to Keep the Car for a Very Long Time!!

But, NO!! It DIDN'T Sound so great, after the first Synthetic Oil Change!! Now, I burn oil, and have an Engine Knock!! THIS SUCKS!!

What can I do to Fix this?!? WTF?!?

All Master Mechanics out there, PLEASE Help!! <:*)

Answer 1

Synthetic oil flows better in the cold, it flows really well in moderate temps. don`t believe the shadetree mechanics, you dont need it!!

Synthetic oil was originally developed for high performance racing engines. Mobil tried to popularize synthetic oil for passenger vehicles back in the early 1970's. At the time, Mobil was promoting 20K or 25K oil changes with synthetic, but they soon backed down from this. Synthetic oil is a good choice if you have a vehicle with a high performance engine (in fact synthetic is required for many of these engines). It is also a good choice if your vehicle is operated in extremely cold climates. It has higher resistance to breakdown caused by heat and it flows better in extreme cold. Unfortunately for the synthetic oil industry there is virtually no advantage to using synthetic oil in a non-high performance engine that is operated in moderate climates. You probably could go a bit longer between oil changes with a synthetic, i.e. following the normal service schedule even if you fall into the severe service category, but I wouldn't advise this. In short, synthetic may give you the peace of mind of knowing that you are using an oil that is far better than necessary for your vehicle, but it won't reduce wear or extend the life of the engine. The mistake some people make it to wrongly extrapolate these benefits onto normal engines operated in mild climates, with the ultimate lack of any knowledge being manifested with statements such as "synthetics provide 'Peace of Mind,' or 'Cheap Insurance,'" or other such nonsense.

Extended Change Intervals
Most manufacturers of synthetic oil advise users to not exceed the manufacturer's recommended oil change interval. Part of this is self interest (they don't want to be liable for any damage) but the real reason is that synthetic oil, while it does have certain advantages, still becomes contaminated.

Be extremely wary of synthetic oil companies that offer to pay for your repairs if it is determined that their oil and their extended change interval recommendation caused the problem. Think for a moment of the incredible hassle you would have to go through to prove responsibility for an engine problem. Who would pay your legal bills? Who would pay for replacement transportation during the battle? The more bizarre the warranty the poorer the product is a good rule of thumb.

API Certification, Phosphorus & ZDDP
Never use a non-API certified synthetic oil (there are many of these on the market). The problem with the non-API certified synthetics is that they contain too much phosphorus (in the form of the additive ZDDP (Zinc Dialkyl Dithiophosphates)). The API has limited the amount of phosphorus because phosphorus shortens the life of the catalytic converter. These oils are fine for snowmobiles, motorcycles, and older cars that don't have a catalytic converter, and the extra ZDDP does provide additional wear protection. Unfortunately, the marketers of some the non-certified oils do not explicitly and honestly state the reason for the lack of API certification. You can check the status of API certification on the API web site. Be certain to go not just by the manufacturer name but by the actual product as well. This is because a manufacturer will sometimes have both certified and non-certified products. Suffice it to say that Mobil 1, Royal Purple, Castrol, & Havoline all make synthetic oils that are API certified and that can be purchased at auto parts stores and other retail outlets. Amsoil has one product line, XL-7500 that is API certified, but it's other lines contain too much ZDDP to be certified and should not be used in vehicles with catalytic converters.

Amsoil
Amsoil actually makes some very good products. The negative image of Amsoil is due to their distribution method (MLM) and their marketing approach. If Amsoil products were competitively priced with Mobil 1 and other synthetics, and if I could buy them in a store, I would not hesitate to use their XL-7500 synthetic as opposed to Mobil 1. What upsets me about Amsoil is that they didn't disclose until recently (and then it was by accident) the real reason that their oils (except for XL-7500) are not API certified. In the past they came up with all sorts of bizarre excuses about the reason for their lack of API certification and this greatly contributed to the distrust that people have of the company.

Answer 2

i truly don't think that the knock that you hear is related to the oil. as for it burning oil, that is possible. synthetic oil is actually smaller molecular speaking, it has a greater change to find a spot to leak through, which is also the advantage of using it in an engine ironically, these smaller chains actually means that there are fewer gaps between two surfaces, reducing the friction. but if you are having issues with the oil, double check everything suck as timing and all vacuum lines and so on, then make a decision, stick with the synthetic, or go back to old faithful.

Answer 3

Let's start with your engine knock. Is this a mechanical failure knock (pistons, bearings), or is this an igniton induced knock.
If the synthetic oil was of a lesser weight, then it is possible that the decreased weight (film) now uncovers the wear that was disguised by the thicker oil. If the rings were worn and now you are using a thinner oil, then it is possible that oil control rings can no longer prevent oil bypassing them and traveling up into the combustion chamber where it is burned and may intefere with the ignition process and or foul the plugs

I have used synthetic in all my bowtie blocks and have never experienced abnormal oil usage and or engine failure

Answer 4

You need to drain the synthetic and change back. You may need to drain twice in quick succession. The synthetic oils are not good in used cars. The surfaces inside wear some, the regular oils build up residue some. Adding the synthetic can remove the residue ( and it knocks ), also removing the reaisue can cause external oil leaks ( residue built up instead of leaking ), internally the oil seals may build up residue and the adding of synthetics remove that residue and you get smoke coming from the engine. Also the synthetic oil is molecularly smaller ( thinner ) and squeezes through surfaces the regular oil would not. Good Luck.

Answer 5

One should not hear any noise coming out of a Finley tuned LS1. Their may be a slight ticking noise-around the intake manifold, this are the injectors at work. If you are hearing any metallic knock you are in trouble. One may hear a slight knocking while accelerating, almost like marbles clashing together, this is know as "PINGING" or PING. Usually this is a result of Pre Ignition.. Low octane Gasoline's will create this annoyance that slowly destroys your engine. The Fix. Switch to a higher Octane gasoline, Anything above 89. 92,93 is better,. The gas will last you longer, your car won't ping and you will have better performance.. Hope this helps.. Will.

Answer 6

changing to synthetic will not create a knock.

I have the same motor in my 2002 Z28. You should run synthetic in it all the time. Dealer recommends it.

I would check into other problems causing the knock.

Answer 7

i've heard piston slap a issue with the ls1 engine, regular oil film is a little thicker which would not bring out the sound, which sounds similar to knocking. synthetic oil has a much thinner film, i dont think there is anything wrong with using syn. try using a thicker synthetic. but piston slap is an issue with 90 percent of ls1's in corvette's and f-body's. owned 2 ls1's one had piston slap, one didn't. even the suv's have piston slap. gm claim's piston slap with wont damage engine.

Answer 8

It is important to not change back a forth from synthetic to non, run it for a little while with the synthetic if it keeps up change back.