Synthetic oil no no in 4100

[caddeville]

Well i was told that synthetic oil no good in flat tappet cam V8's, because its too slippery, oil basically slides off the cam while the car sits and that is how extra wear begins. Flat tappet lifters are designed to rotate, because synthetic oil is so thin, yet it doesn't change viscosity?, they may slightly get stuck once in a while also causing more wear, either way, i'll never put synthetic oil into the 4100, i Used AMSoil 15w40, it runs better and quieter on regular 15w40 diesel oil anyway. 65$ an oil change is a waste of money. 25,000miles? Bullshit, my lifters made noise after 3000 miles the way they did with regular oil. I'm going to finish my caddy tomorrow, and i'll make a vid of us starting it for the first time.

[awadecki]

cool...can't wait for the video. if you have any videos of the internals, that'd be great to show, too.

[zentrade]

I`m not sure about the 4.1. Perhaps you were given good info, Not sure. But i have a theory with synthetic oil and its positive benefits...for th 4.9 at least.
After a (happy) year of ownership and reading lots of posts here, i see that one issue with the 4.9`s is fuel injector and fuel pressure regulators. They seem to not last long on these engines, I dont know why.
But that being the case, Synthetic oil could be a huge help in protecting the internals since the fuel issues could lead to the crankcase taking on a little more trace amounts of raw fuel. its my understanding that synthetic oil is a little more impervious to breaking down to this exposure. Granted its probably not a large amount of raw fuel, But more than usual. I noticed before i fixed some injector problems with my car, I was sucking fuel like a jet and when i changed the oil recently,It had a stronger smell of gas. Oil always does have a gas odor to it when you change it as inevitably in every car some trace amounts of raw fuel make it to the crankcase (especially very high mileage engines that were never rebuilt) but mine really had a ,not overwhelming BUT stronger odor of gas.
Although those issues resolved ,I went with synthetic. Mine was an issue of cold weather starting and not wanting to change oil every 3k miles as i think thats a waste. but to each his own. No complaints so far but i havent ran it long. But i think synthetic is good for the fuel issues.

[caddeville]

for roller cams i was told its good, i didn't get a chance to take pics of internals, my camera was dead, i have older pics of the rockers, anyway yeah i'll let you guys know

[dirt_cheap_fleetwood]

I would never put synthetic oil in an older car or a car designed to run on conventional oil. The synthetic oil can seep into seals and gaskets and cause them to swell up, causing leaks and costing a lot o money or time (depending on if you do it yourself or not) to fix.

[zentrade]

The idea going around that gaskets and seals are harmed by synthetic oil appears to a be a rumor. Mobil 1 does cover this myth on their website...Its the last one (scroll down)

http://www.mobiloil.com/USA-English/...ics/Myths.aspx

[ehall]

Synthetics do not cause leaks. The smaller molecules often allow existing leaks to be found more easily, but the leaks were already there. Synthetics are usually harder to burn too, so a dino oil may burn and plug a leak with carbon whereas a synthetic may not, but again the leak was already there and frankly having it plugged up with carbon is not my idea of a good thing.

Some synthetics have seal conditioners, just like some dino oils.

[noahsdad]

I've been using Amsoil in my 4100 for three years now, and categorically disagree with the first post. I've had my oil analyzed by an independent lab at every change (6k intervals), and the results show wear metals significantly reduced at each change. Right now, my 4100 is wearing at a rate that is 62% slower than the average of all gasoline engines tested. That's not some marketing guy from Amsoil, that's the documented fact.

The flat/roller cam argument is a myth. 4100s have a weak cam to begin with, and if the car was ever overheated or blew a head gasket and was driven with oil contaminated by coolant, the cam is usually the first victim. Synth oil is not thinner, or slipperier. The only difference between synth and dino oil is that synth retains it's chemical structure under a wider range of temperature, and tends to not lose viscosity as rapidly over time.

[awadecki]

noahsdad's post about the weak cams is dead on--I've seen it on my car. 6 flat--not rounded, flat--lobes on my car with only 35,000 miles! Another 6 or 7 were rounded, leaving only 4 good lobes. And, it still idled beautifully, it was just low on power.

[C66 Racing]

Originally Posted by dirt_cheap_fleetwood

I would never put synthetic oil in an older car or a car designed to run on conventional oil. The synthetic oil can seep into seals and gaskets and cause them to swell up, causing leaks and costing a lot o money or time (depending on if you do it yourself or not) to fix.

Not exactly a myth, but not exactly true either. What most people don't realize is that the term "synthetic" isn't really defined and there are a wide variety of oils on the market that can be labeled "synthetic". Each behaves differently and it really isn't accurate to make blanket statements about how a synthetic performs without knowing what its basestock is... and that is getting harder and harder to determine as oil companies become more tight lipped about their basestock.

The API has not come out and defined what is "synthetic", but rather, classified oils into five major groups.

Group I base oils are the least refined of all of the groups. They are usually a mix of different hydrocarbon chains with little or no uniformity. While some automotive oils use these stocks, they are generally used in less demanding applications.

Group II base oils are common in mineral based motor oils. They have fair to good performance in the areas of volatility, oxidation stability, wear prevention and flash/fire points. They have only fair performance in areas such as pour point and cold crank viscosity. Group II base stocks are what the majority of engine oils are made from. 3000 mile oil changes are the norm.

Group III base oils are subjected to the highest level of refining of all the mineral oil stocks. Although not chemically engineered, they offer improved performance in a wide range of areas as well as good molecular uniformity and stability. By definition they are considered a synthesized material and can be used in the production of synthetic and semi-synthetic lubricants. Group III is used in the vast majority of full synthetics or synthetic blends. They are superior to group I and II oils but still have limitations. Some formulations are designed for extended oil changes. AMSOIL XL Motor Oils, Castrol Syntec and many others fall into this category.

Group IV are polyalphaolefins (PAO) which are a chemically engineered synthesized basestocks. PAOs offer excellent stability, molecular uniformity and performance over a wide range of lubricating properties. AMSOIL SAE Synthetic Motor Oils and Mobil 1 primarily use group IV basestocks (though recent info posted on the oil forum indicates that Mobil 1 is also now using a significant proportion of Group III basestock). PAO is a much more expensive basestock than the highly refined petroleum oil basestock of Group III.

Group V base oils are also chemically engineered stocks that do not fall into any of the categories previously mentioned. Typical examples of group V stocks are Esters, polyglycols and silicone. Redline uses an ester basestock.

In the 90s, Mobil filed suit against Castrol for falsely advertising Syntec oil as synthetic, when in fact it contained a Group III, highly hydroprocessed mineral (Dino) oil, instead of a chemically synthesized (group IV or V) basestock. Due to the amount that the mineral oil had been chemically changed, the judge decided in Castrol's favor. As a result, any oil containing this highly hydroprocessed mineral (Dino) oil (currently called Group III basestock by the American Petroleum Institute) can be marketed as a synthetic oil. Since the original synthetic basestock (polyalphaolefin or PAO) is much more expensive than the Group III basestock, most of the oil blenders switched to the Group III basestock, which significantly increased their profit margins.

PAO basestock causes engine seals to shrink slightly (not swell as posted above). Ester basestock causes seals to swell slightly. As a result, in the early days of synthetics, seal leakage was common (due to most early synthetics using a PAO basestock) and led to the widely held view today that synthetics will cause seal leaks. However, AMSOIL has been blending synthetics for over 30 years now and today they use a basestock that is predominantly PAO based, but with an ester additive which counteracts the seal shrinkage of the PAO.

For those synthetic oils using a Group III basestock (the majority of synthetic oils on the market today), their performance with regards to seal shrinkage shouldn't notably different from that of mineral based oils as the basestock is just highly processed mineral oil.

And to confirm what Noahsdad posted above, my wife's Chevy Trailblazer with the 5.3L V-8 has been using AMSOIL XL Synthetic 5w30 since it was new is showing wear on the average of 11-75% below Blackstone Labs universal average for that motor family (and this with a 5817 mile oil change interval:
2003 Chevy Trailblazer Used Oil Analysis AMSOIL XL 5w30