Okay so why is it every car I have takes a different Oil ?

And what about the virtues of Synthetic over Convential ? Are they worth it?

My cars range from
Chevy Tahoe takes 5w-30
Sanger Ski Boat takes 10w-30
Ford V10 RV takes 5w-20
Corvette has 10w-30 Synthetic

So is Synthetic worth the price and can I just put 5w-20 in everything with no issues at all ? or should I just keep investing in the oil cartels and buy a different case of all ?

 

You can [and should, IMO] put synthetic oil in all of your engines. Yes, it is definitely worth it: both from the standpoint of cost savings from fewer and less frequent oil changes and because the life of those engines will be greatly improved. Some will say you need an 'adequate amount' of zinc additive in the synthetic oil for your C3 Corvette. I would argue against that position, unless you have a performance build top-end [hi-lift cam, flat tappets, etc.] and you tend to work it hard on regular occasion. Yes, synthetic oils are that much better than organic oils.

{OK...now let the 'fun' begin.}

 

Yes, kind of agreement on that standpoint as well.

What about the different viscosities, do they make that much of a difference ??

 

i would say depends on temperature
unless you are operationg at freezing the 5w30s and 10w30s oils are going to act the same

 

I would encourage you to read the flat-tappet oil thread sticky before you decide to run an API SM or GF-4 synthetic with your flat-tappet cam. There's been enough cam failures since oil formulations changed in 2005 such that you can be 100% sure that you dramatically increase your risk even with a mild cam by choosing the wrong oil.

List of Flat-Tappet Oils

But a synthetic is definitely what you want across the board.

 

You can buy full synthetic oils with added zinc. But, only the C3 has any [potential] need for it.

 

I use synthetic oils in both my Vette and my Camaro. I also encourage my friends and family to do the same if they want to keep their cars running for a long time. Less friction on internal parts, better gas mileage, and a little more power, yes it's worth it.

 

 

I would use at least a 10W-40 in the vette and make sure it has enough zinc. (Amsoil AMO 10W-40 is great) if you choose to use a synthetic.

 

I agree the sticky is full of lots of great information that will help you decide on the correct oil to use.

 

Just keep in mind, the correct oil for a C3 Corvette without a catalytic converter (more zinc) may damage the catalytic converter on your other cars/trucks.

 

I'm sold on synthetics, but keep in mind that the term "synthetic" has not been defined by the API, so not all synthetics are the same. More on that later.

As for your individual applications, they really do all take different oils optimized for that application. Your Tahoe is going to require a modern API SM 5w30 which the API mandates a limit of 800 ppm phosphorus (key anti-wear additive), your boat will require a marine motor oil which has high levels of anti-wear additives along with anti-corrosion additives not found in automotive oils, Ford specs 20 grade oils to help with their cafe so you'd have to go against owner's manual requirements to use the same 5w30 you use in the Tahoe, and the Corvette should use a high ZDDP oil as mentioned above (and you're going to have a tough time finding one off the shelf).

I'm in a similar situation and as a result, stock a lot of oil - one of the reasons I ended up becoming a dealer. I race my 02 Z06 and use race oil, use 5w30 in my Trailblazer, CJ-4 diesel oil in my GMC 3500 HD tow vehicle and CI-4+ diesel oil (higher anti-wear additives than CJ-4) in my RV.

All synthetics are not equal. 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. Red Line 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.

 

A lot of good information!
I have a 71 SB 350/270 - original engine. I don't push it a lot - only nice rides. Based on this string I will move to synthetics.
Should I go for 10w40?

 

Been using Mobil 1 15W-50 in my 69 SB for years now. Full synth, plenty of Zinc, easy to get.

 

There will be a lot of 'chatter' about "good" synthetics, "bad" synthetics, etc, etc...but I don't there's a full synthetic oil made that won't out-do the best organic oil available, as far as lubrication and durability are concerned. There are better synthetic oils, but as far as a normal 'driver' car is concerned, there are no "bad" ones.

 

Been using it (Mobil 1 15W-50) in my '66 SB since I rebuilt it in 1989.

 

Check the oil sticky. There are a few 10W-40 synthetics that will have enough Zinc.

 

Which viscosity of Mobil 1 has enouch zinc to make a difference?
Thanks.

 

I don't know about you guys, but in my 73 and 76 I just use valvoline 10W-30. My dad and I have been autocrossing heavely and running a few high speed events in my 73 since 1994. I change the oil once a year in the spring and we have never had the motor apart. It still runs great and I never see any shavings or contaminates in the oil.

We do use synthetic in my dad's 90 ZR-1, my 98 camaro, dad's 01 5.3L suburban, and my 01 5.3L silverado. Unless you have a high tolerance engine, the synthetic isn't needed and conventional will work just fine in older engines.

 

I'm of the camp that believes you want over 1200 ppm zinc to make a difference. As a data point, the AMSOIL SAE Synthetic 10w40 has have phosphorus on the order of 1265 ppm, and zinc on the order of 1378 ppm.

For comparison, here's a link to Mobil's current listing of phosphorus/zinc in their whole product line. Best bet is their 0w40 which is 1000/1100 in my opinion as I personally feel that their 15w50 has too high a viscosity for most street applications.
http://www.mobiloil.com/USA-English/...duct_Guide.pdf