Interesting ... neighbour bought a 1989 Trans Am years ago for parts. The car had been in a wreck with plenty of front end damage. They pulled the engine and installed it in a late 80's-somewhere in the 90's P-up truck (all stock with fuel injection etc). Before they installed the engine in the truck, they fired it up while it was still in the Trans Am and it smoked like crazy, I mean HUGE. I figured something rediculous had happened like the force of the impact broke some piston rings (I know, makes no sense but it was the only thing I could think of seeing as how the engine ran perfectly before the crash ... he knew the guy he bought the car from). Regardless of whether or not it was a broken ring or not, I suggested that the engine needed to be torn down because that much smoke made it pretty obvious that something bad was going on inside the engine. I step outside the very next day and the engine is purring like a kitten, not even a hint of smoke. I asked what they had done to it ... the answer "changed the oil from synthetic to the regular stuff". That's all they did. Couple years later I won a case of 12 litres of synthetic oil at a car show ... gave the stuff away. I wouldn't have believed that synthetic oil had caused the engine to smoke like that if I hadn't seen it for myself. By the way, that engine ran perfectly for years in that P-up under their ownership, then they sold the truck ... probably still running fine to this day.

I have absolutely zero interest in putting synthetic oil in anything I own ... I could have used the stuff I won in my lawn mower ... nope, not for me.

I've been to the Shell Oil Laboratory in Sarnia on a 5 day seminar about 10 years ago.
We visited the cold weather testing facility across the road and got to see a "mystery car" being tested at -40f. The model & manufacturer were kept under wraps because they rent out the facility to all Makers. They also have an engine shop and test facility that they can test about 10 motors at the same time, then break them down for measure and test.
I use synthetic in everything!

I run "semi" synthetic in my 2010 Suburban but thats it!!! Was going to switch the 64 Catalina 2+2 over but was 'advised" against it,as to "Leaks" The older engines weren't designed to use it, the 52 Poncho got 10 W30 with "zinc' add. when firing up the fresh SBC. Never even considered it after that.

As most of the guys mentioned, synthetic is a pain in the older style conventional gasketed engines.....leaks yes...the newer engines with mostly printed o-ring type gaskets rarley leak(not saying they dont but for the most part they dont)

We did have a few late model LS eninges that we built that were broken in on regular oil  and the customers switched to synthetic and had oil buring issues.....

Over the years ( building race motors stock cube to 600 inch +) we found the best oil to use was Kendal GT1 we tried everything out there, and after the abuse, upon tear down the only oil that had any viscosity left was the GT1..this is after murdering the engine......were talking a 600 cube with two stages of Nitrous.

We found the GT1 was actually clinging to the engine components when we would tear down..........about mid way through 2003 Kendall did change the formula, the didnt seam to be as thick (even though it was the same grade) but it still worked better then the other brands....just an my opinion......

given the limited benefits of synthetics in older engines, theres little point in spending 4 times the money.  the amount of oil my rides leak and or burn, topping up with synthetics could get pricey as well.  a synthetic blend is cheaper and should give you the best of both worlds if you are bent on having the word synthetic in one of your sentences whilst you are describing all the junk that is your rod or custom

DaveM wrote:

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 The molecules in synthetic oil are smaller. This is why it can show leaks that aren't there with regular oil. Smaller molecules also get into places better. Some seals and hoses aren't happy with the smaller molecules.

I have 2 cars that came from the factory with synthetic, and they always get Mobil-1 full synthetic.

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This. Often switching to synthetic will result in oil leaks, very common to see. No synthetic for me. 

http://www.carbibles.com/engineoil_bible.html

 

http://www.carbibles.com/engineoil_bible.html

-- Edited by 427CARL on Tuesday 25th of December 2012 11:28:20 PM

Brad Penn Partial Synthetic for my beast

Grumpsbodyworks wrote:

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I changed the oil in my hot rod to full synthetic....and now every now and then huffs oil smoke out the exhaust.

Im changing back to a quality regular oil and I'll let you know if it stops.

Anyone else with this problem?

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        maybe rings are sealed yet  

I bought an engine from Phoenix Engines down in Arizona three years ago,the wrapper around the engine had a few precautions attached to it, one of them was not to use synthetic oil in the engine.I presumed it was something to do with the flat tappet cam installed in the engine,the wrapper sticker also stated that not using a zinc additive would void the warranty.Must say I am very pleased with the quality of the engine, would highly recommend this company.